SkCanvas Reference
===
# Canvas
## Overview
## Subtopic
| name | description |
| --- | --- |
| Class or Struct | embedded struct and class members |
| Constant | enum and enum class, const values |
| Constructor | functions that construct SkCanvas |
| Member Function | static functions and member methods |
| Related Function | similar methods grouped together |
# Class SkCanvas
Canvas provides an interface for drawing, and how the drawing is clipped and transformed.
Canvas contains a stack of Matrix and Clip values.
Canvas and Paint together provide the state to draw into Surface or Device.
Each Canvas draw call transforms the geometry of the object by the concatenation of all
Matrix values in the stack. The transformed geometry is clipped by the intersection
of all of Clip values in the stack. The Canvas draw calls use Paint to supply drawing
state such as Color, Typeface, text size, stroke width, Shader and so on.
To draw to a pixel-based destination, create Raster Surface or GPU Surface.
Request Canvas from Surface to obtain the interface to draw.
Canvas generated by Raster Surface draws to memory visible to the CPU.
Canvas generated by GPU Surface uses Vulkan or OpenGL to draw to the GPU.
To draw to a document, obtain Canvas from SVG Canvas, Document PDF, or Picture Recorder.
Document based Canvas and other Canvas Subclasses reference Device describing the
destination.
Canvas can be constructed to draw to Bitmap without first creating Raster Surface.
This approach may be deprecated in the future.
## Related Function
| name | description |
| --- | --- |
| Clip | stack of clipping Paths |
| Draw | draws into Canvas |
| Draw Image | draws Image to Canvas |
| Draw Text | draws text into Canvas |
| Layer | temporary Bitmap to draw into |
| Matrix | coordinate transformation |
| Pixels | read and write pixel values |
| Property | metrics and attributes |
| State Stack | stack of state for hierarchical drawing |
| Utility | rarely called management functions |
## Constant
| name | description |
| --- | --- |
| ColorBehavior | Android framework only |
| PointMode | sets drawPoints options |
| SrcRectConstraint | sets drawImageRect options |
| _anonymous | sets SaveLayerRec options |
## Class or Struct
| name | description |
| --- | --- |
| Lattice | divides Bitmap or Image into a rectangular grid |
| SaveLayerRec | contains the state used to create the Layer |
## Constructor
Create the desired type of Surface to obtain its Canvas when possible. Useful
when no Surface is required, and some helpers implicitly create Raster Surface.
| name | description |
| --- | --- |
| MakeRasterDirect | creates from SkImageInfo and Pixel Storage |
| MakeRasterDirectN32 | creates from image data and Pixel Storage |
| SkCanvas() | creates with no Surface, no dimensions |
| SkCanvas(const SkBitmap& bitmap) | uses existing Bitmap |
| SkCanvas(const SkBitmap& bitmap, ColorBehavior behavior) | Android framework only |
| SkCanvas(const SkBitmap& bitmap, const SkSurfaceProps& props) | uses existing Bitmap and Surface Properties |
| SkCanvas(int width, int height, const SkSurfaceProps* props = nullptr) | no Surface, set dimensions, Surface Properties |
| makeSurface | creates Surface matching SkImageInfo and SkSurfaceProps |
| ~SkCanvas() | draws saved Layers, frees resources |
## Member Function
| name | description |
| --- | --- |
| MakeRasterDirect | creates from SkImageInfo and Pixel Storage |
| MakeRasterDirectN32 | creates from image data and Pixel Storage |
| accessTopLayerPixels | returns writable pixel access if available |
| accessTopRasterHandle | returns context that tracks Clip and Matrix |
| androidFramework setDeviceClipRestriction | for use by Android framework |
| clear | fills Clip with Color |
| clipPath | combines Clip with Path |
| clipRRect | combines Clip with Round Rect |
| clipRect | combines Clip with Rect |
| clipRegion | combines Clip with Region |
| concat | multiplies Matrix by Matrix |
| discard | makes Canvas contents undefined |
| drawAnnotation | associates a Rect with a key-value pair |
| drawArc | draws Arc using Clip, Matrix, and Paint |
| drawAtlas | draws sprites using Clip, Matrix, and Paint |
| drawBitmap | draws Bitmap at (x, y) position |
| drawBitmapLattice | draws proportionally stretched Bitmap |
| drawBitmapNine | draws Nine Patch Bitmap |
| drawBitmapRect | draws Bitmap, source Rect to destination Rect |
| drawCircle | draws Circle using Clip, Matrix, and Paint |
| drawColor | fills Clip with Color and Blend Mode |
| drawDRRect | draws double Round Rect stroked or filled |
| drawDrawable | draws Drawable, encapsulated drawing commands |
| drawIRect | draws IRect using Clip, Matrix, and Paint |
| drawImage | draws Image at (x, y) position |
| drawImageLattice | draws proportionally stretched Image |
| drawImageNine | draws Nine Patch Image |
| drawImageRect | draws Image, source Rect to destination Rect |
| drawLine | draws line segment between two points |
| drawOval | draws Oval using Clip, Matrix, and Paint |
| drawPaint | fills Clip with Paint |
| drawPatch | draws Coons_Patch |
| drawPath | draws Path using Clip, Matrix, and Paint |
| drawPicture | draws Picture using Clip and Matrix |
| drawPoint | draws point at (x, y) position |
| drawPoints | draws array as points, lines, polygon |
| drawPosText | draws text at array of (x, y) positions |
| drawPosTextH | draws text at x positions with common baseline |
| drawRRect | draws Round Rect using Clip, Matrix, and Paint |
| drawRect | draws Rect using Clip, Matrix, and Paint |
| drawRegion | draws Region using Clip, Matrix, and Paint |
| drawRoundRect | draws Round Rect using Clip, Matrix, and Paint |
| drawString | draws null terminated string at (x, y) using font advance |
| drawText | draws text at (x, y), using font advance |
| drawTextBlob | draws text with arrays of positions and Paint |
| drawTextOnPath | draws text following Path contour |
| drawTextOnPathHV | draws text following Path with offsets |
| drawTextRSXform | draws text with array of RSXform |
| drawVertices | draws Vertices, a triangle mesh |
| flush | triggers execution of all pending draw operations |
| getBaseLayerSize | returns size of base Layer in global coordinates |
| getDeviceClipBounds | returns IRect bounds of Clip |
| getGrContext | returns GPU Context of the GPU Surface |
| getLocalClipBounds | returns Clip bounds in source coordinates |
| getMetaData | associates additional data with the canvas |
| getProps | copies Surface Properties if available |
| getSaveCount | returns depth of stack containing Clip and Matrix |
| getTotalMatrix | returns Matrix |
| imageInfo | returns Image Info for Canvas |
| isClipEmpty | returns if Clip is empty |
| isClipRect | returns if Clip is Rect and not empty |
| makeSurface | creates Surface matching SkImageInfo and SkSurfaceProps |
| peekPixels | returns if Canvas has direct access to its pixels |
| quickReject | returns if Rect is outside Clip |
| readPixels | copies and converts rectangle of pixels from Canvas |
| resetMatrix | resets Matrix to identity |
| restore | restores changes to Clip and Matrix, pops save stack |
| restoreToCount | restores changes to Clip and Matrix to given depth |
| rotate | rotates Matrix |
| save | saves Clip and Matrix on stack |
| saveLayer | saves Clip and Matrix on stack; creates Layer |
| saveLayerAlpha | saves Clip and Matrix on stack; creates Layer; sets opacity |
| saveLayerPreserveLCDTextRequests | saves Clip and Matrix on stack; creates Layer for LCD text |
| scale | scales Matrix |
| setAllowSimplifyClip | experimental |
| setMatrix | sets Matrix |
| skew | skews Matrix |
| translate | translates Matrix |
| writePixels | copies and converts rectangle of pixels to Canvas |
## MakeRasterDirect
static std::unique_ptr<SkCanvas> MakeRasterDirect(const SkImageInfo& info, void* pixels,
size_t rowBytes,
const SkSurfaceProps* props = nullptr)
Allocates raster Canvas that will draw directly into pixels.
Canvas is returned if all parameters are valid.
Valid parameters include:
info dimensions are zero or positive;
info contains Color Type and Alpha Type supported by Raster Surface;
pixels is not nullptr;
rowBytes is zero or large enough to contain info width pixels of Color Type.
Pass zero for rowBytes to compute rowBytes from info width and size of pixel.
If rowBytes is greater than zero, it must be equal to or greater than
info width times bytes required for Color Type.
Pixel buffer size should be info height times computed rowBytes.
Pixels are not initialized.
To access pixels after drawing, call flush or peekPixels.
### Parameters
### Return Value
Canvas if all parameters are valid; otherwise, nullptr
### Example
Allocates a three by three bitmap, clears it to white, and draws a black pixel
in the center.
#### Example Output
~~~~
---
-x-
---
~~~~
### See Also
MakeRasterDirectN32 SkSurface::MakeRasterDirect
---
## MakeRasterDirectN32
static std::unique_ptr<SkCanvas> MakeRasterDirectN32(int width, int height, SkPMColor* pixels,
size_t rowBytes)
Allocates raster Canvas specified by inline image specification. Subsequent Canvas
calls draw into pixels.
Color Type is set to kN32 SkColorType.
Alpha Type is set to kPremul SkAlphaType.
To access pixels after drawing, call flush or peekPixels.
Canvas is returned if all parameters are valid.
Valid parameters include:
width and height are zero or positive;
pixels is not nullptr;
rowBytes is zero or large enough to contain width pixels of kN32 SkColorType.
Pass zero for rowBytes to compute rowBytes from width and size of pixel.
If rowBytes is greater than zero, it must be equal to or greater than
width times bytes required for Color Type.
Pixel buffer size should be height times rowBytes.
### Parameters
### Return Value
Canvas if all parameters are valid; otherwise, nullptr
### Example
Allocates a three by three bitmap, clears it to white, and draws a black pixel
in the center.
#### Example Output
~~~~
---
-x-
---
~~~~
### See Also
MakeRasterDirect SkSurface::MakeRasterDirect SkImageInfo::MakeN32Premul[2]
---
## SkCanvas
SkCanvas()
Creates an empty Canvas with no backing device or pixels, with
a width and height of zero.
### Return Value
empty Canvas
### Example
Passes a placeholder to a function that requires one.
#### Example Output
~~~~
paint draws text left to right
paint draws text top to bottom
paint draws text top to bottom
~~~~
### See Also
MakeRasterDirect SkRasterHandleAllocator::MakeCanvas SkSurface::getCanvas SkCreateColorSpaceXformCanvas
---
## SkCanvas
SkCanvas(int width, int height, const SkSurfaceProps* props = nullptr)
Creates Canvas of the specified dimensions without a Surface.
Used by Subclasses with custom implementations for draw methods.
If props equals nullptr, Surface Properties are created with
Surface Properties Legacy Font Host settings, which choose the pixel striping
direction and order. Since a platform may dynamically change its direction when
the device is rotated, and since a platform may have multiple monitors with
different characteristics, it is best not to rely on this legacy behavior.
### Parameters
width |
zero or greater |
height |
zero or greater |
props |
LCD striping orientation and setting for device independent fonts;
may be nullptr |
### Return Value
Canvas placeholder with dimensions
### Example
#### Example Output
~~~~
canvas is empty
~~~~
### See Also
MakeRasterDirect SkSurfaceProps SkPixelGeometry SkCreateColorSpaceXformCanvas
---
## SkCanvas
explicit SkCanvas(SkBaseDevice* device)
soon
---
## SkCanvas
explicit SkCanvas(const SkBitmap& bitmap)
Construct a canvas that draws into bitmap.
Sets SkSurfaceProps::kLegacyFontHost InitType in constructed Surface.
Bitmap is copied so that subsequently editing bitmap will not affect
constructed Canvas.
May be deprecated in the future.
### Parameters
### Return Value
Canvas that can be used to draw into bitmap
### Example
The actual output depends on the installed fonts.
#### Example Output
~~~~
-----
---x-
---x-
---x-
---x-
---x-
---x-
-----
---x-
---x-
-----
~~~~
### See Also
MakeRasterDirect SkRasterHandleAllocator::MakeCanvas SkSurface::getCanvas SkCreateColorSpaceXformCanvas
---
## Enum SkCanvas::ColorBehavior
enum class ColorBehavior {
kLegacy,
};
### Constants
## SkCanvas
SkCanvas(const SkBitmap& bitmap, ColorBehavior behavior)
### Parameters
bitmap |
specifies a bitmap for the canvas to draw into |
behavior |
specializes this constructor; value is unused |
### Return Value
Canvas that can be used to draw into bitmap
---
## SkCanvas
SkCanvas(const SkBitmap& bitmap, const SkSurfaceProps& props)
Construct a canvas that draws into bitmap.
Use props to match the device characteristics, like LCD striping.
bitmap is copied so that subsequently editing bitmap will not affect
constructed Canvas.
### Parameters
### Return Value
Canvas that can be used to draw into bitmap
### Example
The actual output depends on the installed fonts.
#### Example Output
~~~~
-----
---x-
---x-
---x-
---x-
---x-
---x-
-----
---x-
---x-
-----
~~~~
### See Also
MakeRasterDirect SkRasterHandleAllocator::MakeCanvas SkSurface::getCanvas SkCreateColorSpaceXformCanvas
---
## ~SkCanvas
virtual ~SkCanvas()
Draws saved Layers, if any.
Frees up resources used by Canvas.
### Example
Canvas Layer draws into bitmap.
saveLayerAlpha sets up an additional
drawing surface that blends with the bitmap. When
Layer goes out of
scope,
Layer Destructor is called. The saved
Layer is restored, drawing
transparent letters.
### See Also
State Stack
---
## Property
| name | description |
| --- | --- |
| getBaseLayerSize | returns size of base Layer in global coordinates |
| getGrContext | returns GPU Context of the GPU Surface |
| getMetaData | associates additional data with the canvas |
| getProps | copies Surface Properties if available |
| imageInfo | returns Image Info for Canvas |
| isClipEmpty | returns if Clip is empty |
| isClipRect | returns if Clip is Rect and not empty |
## getMetaData
SkMetaData& getMetaData()
Returns storage to associate additional data with the canvas.
The storage is freed when Canvas is deleted.
### Return Value
storage that can be read from and written to
### Example
#### Example Output
~~~~
before: (null)
during: Hello!
after: (null)
~~~~
### See Also
SkMetaData
---
## imageInfo
SkImageInfo imageInfo() const
Returns Image Info for Canvas. If Canvas is not associated with Raster Surface or
GPU Surface, returned Color Type is set to kUnknown SkColorType.
### Return Value
dimensions and Color Type of Canvas
### Example
#### Example Output
~~~~
emptyInfo == canvasInfo
~~~~
### See Also
SkImageInfo MakeRasterDirect makeSurface
---
## getProps
bool getProps(SkSurfaceProps* props) const
If Canvas is associated with Raster Surface or
GPU Surface, copies Surface Properties and returns true. Otherwise,
return false and leave props unchanged.
### Parameters
### Return Value
true if Surface Properties was copied
### Example
#### Example Output
~~~~
isRGB:0
isRGB:1
~~~~
### See Also
SkSurfaceProps makeSurface
---
## Utility
| name | description |
| --- | --- |
| accessTopLayerPixels | returns writable pixel access if available |
| accessTopRasterHandle | returns context that tracks Clip and Matrix |
| discard | makes Canvas contents undefined |
| flush | triggers execution of all pending draw operations |
## flush
void flush()
Triggers the immediate execution of all pending draw operations.
If Canvas is associated with GPU Surface, resolves all pending GPU operations.
If Canvas is associated with Raster Surface, has no effect; raster draw
operations are never deferred.
### See Also
peekPixels SkSurface::flush() GrContext::flush() SkSurface::prepareForExternalIO GrContext::abandonContext()
---
## getBaseLayerSize
virtual SkISize getBaseLayerSize() const
Gets the size of the base or root Layer in global canvas coordinates. The
origin of the base Layer is always (0,0). The area available for drawing may be
smaller (due to clipping or saveLayer).
### Return Value
integral width and height of base Layer
### Example
#### Example Output
~~~~
clip=10,30
size=20,30
~~~~
### See Also
getDeviceClipBounds[2]
---
## makeSurface
sk_sp<SkSurface> makeSurface(const SkImageInfo& info, const SkSurfaceProps* props = nullptr)
Creates Surface matching info and props, and associates it with Canvas.
Returns nullptr if no match found.
If props is nullptr, matches Surface Properties in Canvas. If props is nullptr and Canvas
does not have Surface Properties, creates Surface with default Surface Properties.
### Parameters
### Return Value
Surface matching info and props, or nullptr if no match is available
### Example
#### Example Output
~~~~
compatible != nullptr
size = 3, 4
~~~~
### See Also
SkSurface SkSurface::makeSurface SkImageInfo SkSurfaceProps
---
## getGrContext
virtual GrContext* getGrContext()
Returns GPU Context of the GPU Surface associated with Canvas.
### Return Value
GPU Context, if available; nullptr otherwise
### Example
### See Also
GrContext
---
## accessTopLayerPixels
void* accessTopLayerPixels(SkImageInfo* info, size_t* rowBytes, SkIPoint* origin = nullptr)
Returns the pixel base address, Image Info, rowBytes, and origin if the pixels
can be read directly. The returned address is only valid
while Canvas is in scope and unchanged. Any Canvas call or Surface call
may invalidate the returned address and other returned values.
If pixels are inaccessible, info, rowBytes, and origin are unchanged.
### Parameters
### Return Value
address of pixels, or nullptr if inaccessible
### Example
### Example
Draws "" on the device. Then draws "" in
Layer, and reads
Layer to add a large dotted "". Finally blends
Layer with the
device.
The
Layer and blended result appear on the CPU and GPU but the large dotted
"" appear only on the CPU.
### See Also
SkImageInfo SkPixmap
---
## accessTopRasterHandle
SkRasterHandleAllocator::Handle accessTopRasterHandle() const
Returns custom context that tracks the Matrix and Clip.
Use Raster Handle Allocator to blend Skia drawing with custom drawing, typically performed
by the host platform user interface. The custom context returned is generated by
SkRasterHandleAllocator::MakeCanvas, which creates a custom canvas with raster storage for
the drawing destination.
### Return Value
context of custom allocation
### Example
#### Example Output
~~~~
context = skia
~~~~
### See Also
SkRasterHandleAllocator
---
## Pixels
| name | description |
| --- | --- |
| peekPixels | returns if Canvas has direct access to its pixels |
| readPixels | copies and converts rectangle of pixels from Canvas |
| | readPixels(const SkImageInfo& dstInfo, void* dstPixels, size t dstRowBytes, int srcX, int srcY) |
| | readPixels(const SkPixmap& pixmap, int srcX, int srcY) |
| | readPixels(const SkBitmap& bitmap, int srcX, int srcY) |
| writePixels | copies and converts rectangle of pixels to Canvas |
| | writePixels(const SkImageInfo& info, const void* pixels, size t rowBytes, int x, int y) |
| | writePixels(const SkBitmap& bitmap, int x, int y) |
## peekPixels
bool peekPixels(SkPixmap* pixmap)
Returns true if Canvas has direct access to its pixels.
Pixels are readable when Device is raster. Pixels are not readable when Canvas
is returned from GPU Surface, returned by SkDocument::beginPage, returned by
SkPictureRecorder::beginRecording, or Canvas is the base of a utility class
like SkDumpCanvas.
pixmap is valid only while Canvas is in scope and unchanged. Any
Canvas or Surface call may invalidate the pixmap values.
### Parameters
pixmap |
storage for pixel state if pixels are readable; otherwise, ignored |
### Return Value
true if Canvas has direct access to pixels
### Example
#### Example Output
~~~~
width=256 height=256
~~~~
### See Also
readPixels[2][3] SkBitmap::peekPixels SkImage::peekPixels SkSurface::peekPixels
---
## readPixels
bool readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes, int srcX, int srcY)
Copies Rect of pixels from Canvas into dstPixels. Matrix and Clip are
ignored.
Source Rect corners are (srcX, srcY) and (imageInfo.width(), imageInfo.height()).
Destination Rect corners are (0, 0) and (dstInfo.width(), dstInfo.height()).
Copies each readable pixel intersecting both rectangles, without scaling,
converting to dstInfo.colorType() and dstInfo.alphaType() if required.
Pixels are readable when Device is raster, or backed by a GPU.
Pixels are not readable when SkCanvas is returned by SkDocument::beginPage,
returned by SkPictureRecorder::beginRecording, or Canvas is the base of a utility
class like SkDumpCanvas.
The destination pixel storage must be allocated by the caller.
Pixel values are converted only if Color Type and Alpha Type
do not match. Only pixels within both source and destination rectangles
are copied. dstPixels contents outside Rect intersection are unchanged.
Pass negative values for srcX or srcY to offset pixels across or down destination.
Does not copy, and returns false if:
Source and destination rectangles do not intersect. |
Canvas pixels could not be converted to dstInfo.colorType() or dstInfo.alphaType(). |
Canvas pixels are not readable; for instance, Canvas is document-based. |
dstRowBytes is too small to contain one row of pixels. |
### Parameters
### Return Value
true if pixels were copied
### Example
A black circle drawn on a blue background provides an image to copy.
readPixels copies one quarter of the canvas into each of the four corners.
The copied quarter circles overdraw the original circle.
### Example
#### Example Output
~~~~
pixel = 802b5580
pixel = 8056a9ff
~~~~
### See Also
peekPixels writePixels[2] drawBitmap drawImage[2] SkBitmap::readPixels[2][3][4] SkPixmap::readPixels[2][3][4][5] SkImage::readPixels[2] SkSurface::readPixels[2][3]
---
bool readPixels(const SkPixmap& pixmap, int srcX, int srcY)
Copies Rect of pixels from Canvas into pixmap. Matrix and Clip are
ignored.
Source Rect corners are (srcX, srcY) and (imageInfo.width(), imageInfo.height()).
Destination Rect corners are (0, 0) and (pixmap.width(), pixmap.height()).
Copies each readable pixel intersecting both rectangles, without scaling,
converting to pixmap.colorType() and pixmap.alphaType() if required.
Pixels are readable when Device is raster, or backed by a GPU.
Pixels are not readable when SkCanvas is returned by SkDocument::beginPage,
returned by SkPictureRecorder::beginRecording, or Canvas is the base of a utility
class like SkDumpCanvas.
Caller must allocate pixel storage in pixmap if needed.
Pixel values are converted only if Color Type and Alpha Type
do not match. Only pixels within both source and destination Rects
are copied. pixmap pixels contents outside Rect intersection are unchanged.
Pass negative values for srcX or srcY to offset pixels across or down pixmap.
Does not copy, and returns false if:
Source and destination rectangles do not intersect. |
Canvas pixels could not be converted to pixmap.colorType() or pixmap.alphaType(). |
Canvas pixels are not readable; for instance, Canvas is document-based. |
Pixmap pixels could not be allocated. |
pixmap.rowBytes() is too small to contain one row of pixels. |
### Parameters
pixmap |
storage for pixels copied from Canvas |
srcX |
offset into readable pixels in x; may be negative |
srcY |
offset into readable pixels in y; may be negative |
### Return Value
true if pixels were copied
### Example
#### Example Output
~~~~
pixel = 802b5580
~~~~
### See Also
peekPixels writePixels[2] drawBitmap drawImage[2] SkBitmap::readPixels[2][3][4] SkPixmap::readPixels[2][3][4][5] SkImage::readPixels[2] SkSurface::readPixels[2][3]
---
bool readPixels(const SkBitmap& bitmap, int srcX, int srcY)
Copies Rect of pixels from Canvas into bitmap. Matrix and Clip are
ignored.
Source Rect corners are (srcX, srcY) and (imageInfo.width(), imageInfo.height()).
Destination Rect corners are (0, 0) and (bitmap.width(), bitmap.height()).
Copies each readable pixel intersecting both rectangles, without scaling,
converting to bitmap.colorType() and bitmap.alphaType() if required.
Pixels are readable when Device is raster, or backed by a GPU.
Pixels are not readable when SkCanvas is returned by SkDocument::beginPage,
returned by SkPictureRecorder::beginRecording, or Canvas is the base of a utility
class like SkDumpCanvas.
Caller must allocate pixel storage in bitmap if needed.
Bitmap values are converted only if Color Type and Alpha Type
do not match. Only pixels within both source and destination rectangles
are copied. Bitmap pixels outside Rect intersection are unchanged.
Pass negative values for srcX or srcY to offset pixels across or down bitmap.
Does not copy, and returns false if:
Source and destination rectangles do not intersect. |
Canvas pixels could not be converted to bitmap.colorType() or bitmap.alphaType(). |
Canvas pixels are not readable; for instance, Canvas is document-based. |
bitmap pixels could not be allocated. |
bitmap.rowBytes() is too small to contain one row of pixels. |
### Parameters
bitmap |
storage for pixels copied from Canvas |
srcX |
offset into readable pixels in x; may be negative |
srcY |
offset into readable pixels in y; may be negative |
### Return Value
true if pixels were copied
### Example
#### Example Output
~~~~
pixel = 802b5580
~~~~
### See Also
peekPixels writePixels[2] drawBitmap drawImage[2] SkBitmap::readPixels[2][3][4] SkPixmap::readPixels[2][3][4][5] SkImage::readPixels[2] SkSurface::readPixels[2][3]
---
## writePixels
bool writePixels(const SkImageInfo& info, const void* pixels, size_t rowBytes, int x, int y)
Copies Rect from pixels to Canvas. Matrix and Clip are ignored.
Source Rect corners are (0, 0) and (info.width(), info.height()).
Destination Rect corners are (x, y) and
(imageInfo.width(), imageInfo.height()).
Copies each readable pixel intersecting both rectangles, without scaling,
converting to imageInfo.colorType() and imageInfo.alphaType() if required.
Pixels are writable when Device is raster, or backed by a GPU.
Pixels are not writable when SkCanvas is returned by SkDocument::beginPage,
returned by SkPictureRecorder::beginRecording, or Canvas is the base of a utility
class like SkDumpCanvas.
Pixel values are converted only if Color Type and Alpha Type
do not match. Only pixels within both source and destination rectangles
are copied. Canvas pixels outside Rect intersection are unchanged.
Pass negative values for x or y to offset pixels to the left or
above Canvas pixels.
Does not copy, and returns false if:
### Parameters
### Return Value
true if pixels were written to Canvas
### Example
### See Also
readPixels[2][3] drawBitmap drawImage[2] SkBitmap::writePixels[2][3]
---
bool writePixels(const SkBitmap& bitmap, int x, int y)
Copies Rect from pixels to Canvas. Matrix and Clip are ignored.
Source Rect corners are (0, 0) and (bitmap.width(), bitmap.height()).
Destination Rect corners are (x, y) and
(imageInfo.width(), imageInfo.height()).
Copies each readable pixel intersecting both rectangles, without scaling,
converting to imageInfo.colorType() and imageInfo.alphaType() if required.
Pixels are writable when Device is raster, or backed by a GPU.
Pixels are not writable when SkCanvas is returned by SkDocument::beginPage,
returned by SkPictureRecorder::beginRecording, or Canvas is the base of a utility
class like SkDumpCanvas.
Pixel values are converted only if Color Type and Alpha Type
do not match. Only pixels within both source and destination rectangles
are copied. Canvas pixels outside Rect intersection are unchanged.
Pass negative values for x or y to offset pixels to the left or
above Canvas pixels.
Does not copy, and returns false if:
Source and destination rectangles do not intersect. |
bitmap does not have allocated pixels. |
bitmap pixels could not be converted to Canvas imageInfo.colorType() or
imageInfo.alphaType(). |
Canvas pixels are not writable; for instance, Canvas is document based. |
bitmap pixels are inaccessible; for instance, bitmap wraps a texture. |
### Parameters
bitmap |
contains pixels copied to Canvas |
x |
offset into Canvas writable pixels in x; may be negative |
y |
offset into Canvas writable pixels in y; may be negative |
### Return Value
true if pixels were written to Canvas
### Example
### See Also
readPixels[2][3] drawBitmap drawImage[2] SkBitmap::writePixels[2][3]
---
## State Stack
Canvas maintains a stack of state that allows hierarchical drawing, commonly used
to implement windows and views. The initial state has an identity matrix and and
an infinite clip. Even with a wide-open clip, drawing is constrained by the
bounds of the Canvas Surface or Device.
Canvas savable state consists of Clip, Matrix, and Draw Filter.
Clip describes the area that may be drawn to.
Matrix transforms the geometry.
Draw Filter (deprecated on most platforms) modifies the paint before drawing.
save, saveLayer, saveLayerPreserveLCDTextRequests, and saveLayerAlpha
save state and return the depth of the stack.
restore, restoreToCount, and
### Example
Draw to ever smaller clips; then restore drawing to full canvas.
Note that the second
clipRect is not permitted to enlarge
Clip.
Each Clip uses the current Matrix for its coordinates.
### Example
While
clipRect is given the same rectangle twice,
Matrix makes the second
clipRect draw at half the size of the first.
### See Also
save saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha restore restoreToCount
## save
int save()
Saves Matrix, Clip, and Draw Filter (Draw Filter deprecated on most platforms).
Calling restore discards changes to Matrix, Clip, and Draw Filter,
restoring the Matrix, Clip, and Draw Filter to their state when save was called.
Matrix may be changed by translate, scale, rotate, skew, concat, setMatrix,
and resetMatrix. Clip may be changed by clipRect, clipRRect, clipPath, clipRegion.
Saved Canvas state is put on a stack; multiple calls to save should be balance
by an equal number of calls to restore.
Call restoreToCount with result to restore this and subsequent saves.
### Return Value
depth of saved stack
### Example
The black square is translated 50 pixels down and to the right.
Restoring
Canvas state removes
translate from
Canvas stack;
the red square is not translated, and is drawn at the origin.
### See Also
saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha restore restoreToCount
---
## restore
void restore()
Removes changes to Matrix, Clip, and Draw Filter since Canvas state was
last saved. The state is removed from the stack.
Does nothing if the stack is empty.
### Example
### See Also
save saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha restoreToCount
---
## getSaveCount
int getSaveCount() const
Returns the number of saved states, each containing: Matrix, Clip, and Draw Filter.
Equals the number of save calls less the number of restore calls plus one.
The save count of a new canvas is one.
### Return Value
depth of save state stack
### Example
#### Example Output
~~~~
depth = 1
depth = 2
depth = 1
~~~~
### See Also
save restore restoreToCount
---
## restoreToCount
void restoreToCount(int saveCount)
Restores state to Matrix, Clip, and Draw Filter values when save, saveLayer,
saveLayerPreserveLCDTextRequests, or saveLayerAlpha returned saveCount.
Does nothing if saveCount is greater than state stack count.
Restores state to initial values if saveCount is less than or equal to one.
### Parameters
### Example
#### Example Output
~~~~
depth = 1
depth = 3
depth = 1
~~~~
### See Also
restore getSaveCount save
---
## Layer
Layer allocates a temporary Bitmap to draw into. When the drawing is
complete, the Bitmap is drawn into the Canvas.
Layer is saved in a stack along with other saved state. When state with a Layer
is restored, the Bitmap is drawn into the previous Layer.
Layer may be initialized with the contents of the previous Layer. When Layer is
restored, its Bitmap can be modified by Paint passed to Layer to apply
Color Alpha, Color Filter, Image Filter, and Blend Mode.
## saveLayer
int saveLayer(const SkRect* bounds, const SkPaint* paint)
Saves Matrix, Clip, and Draw Filter (Draw Filter deprecated on most platforms),
and allocates a Bitmap for subsequent drawing.
Calling restore discards changes to Matrix, Clip, and Draw Filter,
and draws the Bitmap.
Matrix may be changed by translate, scale, rotate, skew, concat,
setMatrix, and resetMatrix. Clip may be changed by clipRect, clipRRect,
clipPath, clipRegion.
Rect bounds suggests but does not define the Bitmap size. To clip drawing to
a specific rectangle, use clipRect.
Optional Paint paint applies Color Alpha, Color Filter, Image Filter, and
Blend Mode when restore is called.
Call restoreToCount with returned value to restore this and subsequent saves.
### Parameters
bounds |
hint to limit the size of the Layer; may be nullptr |
paint |
graphics state for Layer; may be nullptr |
### Return Value
depth of saved stack
### Example
### See Also
save restore saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha SaveLayerRec
---
int saveLayer(const SkRect& bounds, const SkPaint* paint)
Saves Matrix, Clip, and Draw Filter (Draw Filter deprecated on most platforms),
and allocates a Bitmap for subsequent drawing.
Calling restore discards changes to Matrix, Clip, and Draw Filter,
and draws the Bitmap.
Matrix may be changed by translate, scale, rotate, skew, concat,
setMatrix, and resetMatrix. Clip may be changed by clipRect, clipRRect,
clipPath, clipRegion.
Rect bounds suggests but does not define the Layer size. To clip drawing to
a specific rectangle, use clipRect.
Optional Paint paint applies Color Alpha, Color Filter, Image Filter, and
Blend Mode when restore is called.
Call restoreToCount with returned value to restore this and subsequent saves.
### Parameters
### Return Value
depth of saved stack
### Example
### See Also
save restore saveLayerPreserveLCDTextRequests saveLayerAlpha SaveLayerRec
---
## saveLayerPreserveLCDTextRequests
int saveLayerPreserveLCDTextRequests(const SkRect* bounds, const SkPaint* paint)
Saves Matrix, Clip, and Draw Filter (Draw Filter deprecated on most platforms),
and allocates a Bitmap for subsequent drawing.
LCD Text is preserved when the Layer is drawn to the prior Layer.
Calling restore discards changes to Matrix, Clip, and Draw Filter,
and draws Layer.
Matrix may be changed by translate, scale, rotate, skew, concat,
setMatrix, and resetMatrix. Clip may be changed by clipRect, clipRRect,
clipPath, clipRegion.
Rect bounds suggests but does not define the Layer size. To clip drawing to
a specific rectangle, use clipRect.
Optional Paint paint applies Color Alpha, Color Filter, Image Filter, and
Blend Mode when restore is called.
Call restoreToCount with returned value to restore this and subsequent saves.
Draw text on an opaque background so that LCD Text blends correctly with the
prior Layer. LCD Text drawn on a background with transparency may result in
incorrect blending.
### Parameters
### Return Value
depth of saved stack
### Example
### See Also
save restore saveLayer[2][3] saveLayerAlpha SaveLayerRec
---
## saveLayerAlpha
int saveLayerAlpha(const SkRect* bounds, U8CPU alpha)
Saves Matrix, Clip, and Draw Filter (Draw Filter deprecated on most platforms),
and allocates Bitmap for subsequent drawing.
Calling restore discards changes to Matrix, Clip, and Draw Filter,
and blends Layer with alpha opacity onto prior Layer.
Matrix may be changed by translate, scale, rotate, skew, concat,
setMatrix, and resetMatrix. Clip may be changed by clipRect, clipRRect,
clipPath, clipRegion.
Rect bounds suggests but does not define Layer size. To clip drawing to
a specific rectangle, use clipRect.
alpha of zero is fully transparent, 255 is fully opaque.
Call restoreToCount with returned value to restore this and subsequent saves.
### Parameters
### Return Value
depth of saved stack
### Example
### See Also
save restore saveLayer[2][3] saveLayerPreserveLCDTextRequests SaveLayerRec
---
## Enum SkCanvas::_anonymous
enum {
kPreserveLCDText SaveLayerFlag = 1 << 1,
kInitWithPrevious SaveLayerFlag = 1 << 2,
kDontClipToLayer Legacy SaveLayerFlag = kDontClipToLayer_PrivateSaveLayerFlag,
};
SaveLayerFlags provides options that may be used in any combination in SaveLayerRec,
defining how Layer allocated by saveLayer operates.
### Constants
### Example
Canvas Layer captures red and blue circles scaled up by four.
scalePaint blends
Layer back with transparency.
### See Also
save restore saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha SaveLayerRec
# Struct SkCanvas::SaveLayerRec
struct SaveLayerRec {
SaveLayerRec*(...
const SkRect* fBounds;
const SkPaint* fPaint;
const SkImageFilter* fBackdrop;
SaveLayerFlags fSaveLayerFlags;
};
SaveLayerRec contains the state used to create the Layer.
const SkRect* fBounds
fBounds is used as a hint to limit the size of Layer; may be nullptr.
fBounds suggests but does not define Layer size. To clip drawing to
a specific rectangle, use clipRect.
const SkPaint* fPaint
fPaint modifies how Layer overlays the prior Layer; may be nullptr.
Color Alpha, Blend Mode, Color Filter, Draw Looper, Image Filter, and
Mask Filter affect Layer draw.
const SkImageFilter* fBackdrop
fBackdrop applies Image Filter to the prior Layer when copying to the Layer;
may be nullptr. Use kInitWithPrevious SaveLayerFlag to copy the
prior Layer without an Image Filter.
const SkImage* fClipMask
restore clips Layer by the Color Alpha channel of fClipMask when
Layer is copied to Device. fClipMask may be nullptr. .
const SkMatrix* fClipMatrix
fClipMatrix transforms fClipMask before it clips Layer. If
fClipMask describes a translucent gradient, it may be scaled and rotated
without introducing artifacts. fClipMatrix may be nullptr.
SaveLayerFlags fSaveLayerFlags
fSaveLayerFlags are used to create Layer without transparency,
create Layer for LCD text, and to create Layer with the
contents of the previous Layer.
### Example
Canvas Layer captures a red Anti-aliased circle and a blue
Aliased circle scaled
up by four. After drawing another red circle without scaling on top, the
Layer is
transferred to the main canvas.
## SaveLayerRec
SaveLayerRec()
Sets fBounds, fPaint, and fBackdrop to nullptr. Clears fSaveLayerFlags.
### Return Value
empty SaveLayerRec
### Example
#### Example Output
~~~~
rec1 == rec2
~~~~
### See Also
save restore saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha
---
SaveLayerRec(const SkRect* bounds, const SkPaint* paint, SaveLayerFlags saveLayerFlags = 0)
Sets fBounds, fPaint, and fSaveLayerFlags; sets fBackdrop to nullptr.
### Parameters
### Return Value
SaveLayerRec with empty backdrop
### Example
#### Example Output
~~~~
rec1 == rec2
~~~~
### See Also
save restore saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha
---
SaveLayerRec(const SkRect* bounds, const SkPaint* paint, const SkImageFilter* backdrop,
SaveLayerFlags saveLayerFlags)
Sets fBounds, fPaint, fBackdrop, and fSaveLayerFlags.
### Parameters
### Return Value
SaveLayerRec fully specified
### Example
#### Example Output
~~~~
rec1 == rec2
~~~~
### See Also
save restore saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha
---
SaveLayerRec(const SkRect* bounds, const SkPaint* paint, const SkImageFilter* backdrop,
const SkImage* clipMask, const SkMatrix* clipMatrix, SaveLayerFlags saveLayerFlags)
Not ready for general use.Sets fBounds, fPaint, fBackdrop, fClipMask, fClipMatrix, and fSaveLayerFlags.
clipMatrix uses Color Alpha channel of image, transformed by clipMatrix, to clip
Layer when drawn to Canvas.
Implementation is not complete; has no effect if Device is GPU-backed.
### Parameters
### Return Value
SaveLayerRec fully specified
### See Also
save restore saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha
---
int saveLayer(const SaveLayerRec& layerRec)
Saves Matrix, Clip, and Draw Filter (Draw Filter deprecated on most platforms),
and allocates Bitmap for subsequent drawing.
Calling restore discards changes to Matrix, Clip, and Draw Filter,
and blends Bitmap with Color Alpha opacity onto the prior Layer.
Matrix may be changed by translate, scale, rotate, skew, concat,
setMatrix, and resetMatrix. Clip may be changed by clipRect, clipRRect,
clipPath, clipRegion.
SaveLayerRec contains the state used to create the Layer.
Call restoreToCount with returned value to restore this and subsequent saves.
### Parameters
### Return Value
depth of save state stack
### Example
### See Also
save restore saveLayer[2][3] saveLayerPreserveLCDTextRequests saveLayerAlpha
---
## Matrix
## translate
void translate(SkScalar dx, SkScalar dy)
Translate Matrix by dx along the x-axis and dy along the y-axis.
Mathematically, replace Matrix with a translation matrix
Premultiplied with Matrix.
This has the effect of moving the drawing by (dx, dy) before transforming
the result with Matrix.
### Parameters
dx |
distance to translate in x |
dy |
distance to translate in y |
### Example
scale followed by
translate produces different results from
translate followed
by
scale.
The blue stroke follows translate of (50, 50); a black
fill follows scale of (2, 1/2.f). After restoring the clip, which resets
Matrix, a red frame follows the same scale of (2, 1/2.f); a gray fill
follows translate of (50, 50).
### See Also
concat scale skew rotate[2] setMatrix
---
## scale
void scale(SkScalar sx, SkScalar sy)
Scale Matrix by sx on the x-axis and sy on the y-axis.
Mathematically, replace Matrix with a scale matrix
Premultiplied with Matrix.
This has the effect of scaling the drawing by (sx, sy) before transforming
the result with Matrix.
### Parameters
sx |
amount to scale in x |
sy |
amount to scale in y |
### Example
### See Also
concat translate skew rotate[2] setMatrix
---
## rotate
void rotate(SkScalar degrees)
Rotate Matrix by degrees. Positive degrees rotates clockwise.
Mathematically, replace Matrix with a rotation matrix
Premultiplied with Matrix.
This has the effect of rotating the drawing by degrees before transforming
the result with Matrix.
### Parameters
### Example
Draw clock hands at time 5:10. The hour hand and minute hand point up and
are rotated clockwise.
### See Also
concat translate skew scale setMatrix
---
void rotate(SkScalar degrees, SkScalar px, SkScalar py)
Rotate Matrix by degrees about a point at (px, py). Positive degrees rotates
clockwise.
Mathematically, construct a rotation matrix. Premultiply the rotation matrix by
a translation matrix, then replace Matrix with the resulting matrix
Premultiplied with Matrix.
This has the effect of rotating the drawing about a given point before
transforming the result with Matrix.
### Parameters
degrees |
amount to rotate, in degrees |
px |
x-coordinate of the point to rotate about |
py |
y-coordinate of the point to rotate about |
### Example
### See Also
concat translate skew scale setMatrix
---
## skew
void skew(SkScalar sx, SkScalar sy)
Skew Matrix by sx on the x-axis and sy on the y-axis. A positive value of sx
skews the drawing right as y increases; a positive value of sy skews the drawing
down as x increases.
Mathematically, replace Matrix with a skew matrix Premultiplied with Matrix.
This has the effect of skewing the drawing by (sx, sy) before transforming
the result with Matrix.
### Parameters
sx |
amount to skew in x |
sy |
amount to skew in y |
### Example
Black text mimics an oblique text style by using a negative skew in x that
shifts the geometry to the right as the y values decrease.
Red text uses a positive skew in y to shift the geometry down as the x values
increase.
Blue text combines x and y skew to rotate and scale.
### See Also
concat translate rotate[2] scale setMatrix
---
## concat
void concat(const SkMatrix& matrix)
Replace Matrix with matrix Premultiplied with existing Matrix.
This has the effect of transforming the drawn geometry by matrix, before
transforming the result with existing Matrix.
### Parameters
### Example
### See Also
translate rotate[2] scale skew setMatrix
---
## setMatrix
void setMatrix(const SkMatrix& matrix)
Replace Matrix with matrix.
Unlike concat, any prior matrix state is overwritten.
### Parameters
### Example
### See Also
resetMatrix concat translate rotate[2] scale skew
---
## resetMatrix
void resetMatrix()
Sets Matrix to the identity matrix.
Any prior matrix state is overwritten.
### Example
### See Also
setMatrix concat translate rotate[2] scale skew
---
## getTotalMatrix
const SkMatrix& getTotalMatrix() const
Returns Matrix.
This does not account for translation by Device or Surface.
### Return Value
Matrix in Canvas
### Example
#### Example Output
~~~~
isIdentity true
~~~~
### See Also
setMatrix resetMatrix concat
---
## Clip
Clip is built from a stack of clipping paths. Each Path in the
stack can be constructed from one or more Path Contour elements. The
Path Contour may be composed of any number of Path Verb segments. Each
Path Contour forms a closed area; Path Fill Type defines the area enclosed
by Path Contour.
Clip stack of Path elements successfully restrict the Path area. Each
Path is transformed by Matrix, then intersected with or subtracted from the
prior Clip to form the replacement Clip. Use SkClipOp::kDifference
to subtract Path from Clip; use SkClipOp::kIntersect to intersect Path
with Clip.
A clipping Path may be Anti-aliased; if Path, after transformation, is
composed of horizontal and vertical lines, clearing Anti-alias allows whole pixels
to either be inside or outside the clip. The fastest drawing has a Aliased,
rectangular clip.
If clipping Path has Anti-alias set, clip may partially clip a pixel, requiring
that drawing blend partially with the destination along the edge. A rotated
rectangular Anti-aliased clip looks smoother but draws slower.
Clip can combine with Rect and Round Rect primitives; like
Path, these are transformed by Matrix before they are combined with Clip.
Clip can combine with Region. Region is assumed to be in Device coordinates
and is unaffected by Matrix.
### Example
Draw a red circle with an
Aliased clip and an Anti-aliased clip.
Use an image filter to zoom into the pixels drawn.
The edge of the
Aliased clip fully draws pixels in the red circle.
The edge of the Anti-aliased clip partially draws pixels in the red circle.
## clipRect
void clipRect(const SkRect& rect, SkClipOp op, bool doAntiAlias)
Replace Clip with the intersection or difference of Clip and rect,
with an Aliased or Anti-aliased clip edge. rect is transformed by Matrix
before it is combined with Clip.
### Parameters
### Example
### See Also
clipRRect[2][3] clipPath[2][3] clipRegion
---
void clipRect(const SkRect& rect, SkClipOp op)
Replace Clip with the intersection or difference of Clip and rect.
Resulting Clip is Aliased; pixels are fully contained by the clip.
rect is transformed by Matrix before it is combined with Clip.
### Parameters
### Example
### See Also
clipRRect[2][3] clipPath[2][3] clipRegion
---
void clipRect(const SkRect& rect, bool doAntiAlias = false)
Replace Clip with the intersection of Clip and rect.
Resulting Clip is Aliased; pixels are fully contained by the clip.
rect is transformed by Matrix
before it is combined with Clip.
### Parameters
### Example
A circle drawn in pieces looks uniform when drawn
Aliased.
The same circle pieces blend with pixels more than once when Anti-aliased,
visible as a thin pair of lines through the right circle.
### See Also
clipRRect[2][3] clipPath[2][3] clipRegion
---
## androidFramework_setDeviceClipRestriction
void androidFramework_setDeviceClipRestriction(const SkIRect& rect)
Sets the maximum clip rectangle, which can be set by clipRect, clipRRect and
clipPath and intersect the current clip with the specified rect.
The maximum clip affects only future clipping operations; it is not retroactive.
The clip restriction is not recorded in pictures.
Pass an empty rect to disable maximum clip.
### Parameters
rect |
maximum allowed clip in device coordinates |
#
---
## clipRRect
void clipRRect(const SkRRect& rrect, SkClipOp op, bool doAntiAlias)
Replace Clip with the intersection or difference of Clip and rrect,
with an Aliased or Anti-aliased clip edge.
rrect is transformed by Matrix
before it is combined with Clip.
### Parameters
### Example
### See Also
clipRect[2][3] clipPath[2][3] clipRegion
---
void clipRRect(const SkRRect& rrect, SkClipOp op)
Replace Clip with the intersection or difference of Clip and rrect.
Resulting Clip is Aliased; pixels are fully contained by the clip.
rrect is transformed by Matrix before it is combined with Clip.
### Parameters
### Example
### See Also
clipRect[2][3] clipPath[2][3] clipRegion
---
void clipRRect(const SkRRect& rrect, bool doAntiAlias = false)
Replace Clip with the intersection of Clip and rrect,
with an Aliased or Anti-aliased clip edge.
rrect is transformed by Matrix before it is combined with Clip.
### Parameters
### Example
### See Also
clipRect[2][3] clipPath[2][3] clipRegion
---
## clipPath
void clipPath(const SkPath& path, SkClipOp op, bool doAntiAlias)
Replace Clip with the intersection or difference of Clip and path,
with an Aliased or Anti-aliased clip edge. Path Fill Type determines if path
describes the area inside or outside its contours; and if Path Contour overlaps
itself or another Path Contour, whether the overlaps form part of the area.
path is transformed by Matrix before it is combined with Clip.
### Parameters
### Example
### See Also
clipRect[2][3] clipRRect[2][3] clipRegion
---
void clipPath(const SkPath& path, SkClipOp op)
Replace Clip with the intersection or difference of Clip and path.
Resulting Clip is Aliased; pixels are fully contained by the clip.
Path Fill Type determines if path
describes the area inside or outside its contours; and if Path Contour overlaps
itself or another Path Contour, whether the overlaps form part of the area.
path is transformed by Matrix
before it is combined with Clip.
### Parameters
### Example
### See Also
clipRect[2][3] clipRRect[2][3] clipRegion
---
void clipPath(const SkPath& path, bool doAntiAlias = false)
Replace Clip with the intersection of Clip and path.
Resulting Clip is Aliased; pixels are fully contained by the clip.
Path Fill Type determines if path
describes the area inside or outside its contours; and if Path Contour overlaps
itself or another Path Contour, whether the overlaps form part of the area.
path is transformed by Matrix before it is combined with Clip.
### Parameters
### Example
### See Also
clipRect[2][3] clipRRect[2][3] clipRegion
---
## setAllowSimplifyClip
void setAllowSimplifyClip(bool allow)
Only used for testing.Set to simplify clip stack using PathOps.
---
## clipRegion
void clipRegion(const SkRegion& deviceRgn, SkClipOp op = SkClipOp::kIntersect)
Replace Clip with the intersection or difference of Clip and Region deviceRgn.
Resulting Clip is Aliased; pixels are fully contained by the clip.
deviceRgn is unaffected by Matrix.
### Parameters
### Example
region is unaffected by canvas rotation; iRect is affected by canvas rotation.
Both clips are
Aliased; this is not noticeable on
Region clip because it
aligns to pixel boundaries.
### See Also
clipRect[2][3] clipRRect[2][3] clipPath[2][3]
---
## quickReject
bool quickReject(const SkRect& rect) const
Return true if Rect rect, transformed by Matrix, can be quickly determined to be
outside of Clip. May return false even though rect is outside of Clip.
Use to check if an area to be drawn is clipped out, to skip subsequent draw calls.
### Parameters
### Return Value
true if rect, transformed by Matrix, does not intersect Clip
### Example
#### Example Output
~~~~
quickReject true
quickReject false
~~~~
### See Also
getLocalClipBounds[2] getTotalMatrix SkBitmap::drawsNothing
---
bool quickReject(const SkPath& path) const
Return true if path, transformed by Matrix, can be quickly determined to be
outside of Clip. May return false even though path is outside of Clip.
Use to check if an area to be drawn is clipped out, to skip subsequent draw calls.
### Parameters
### Return Value
true if path, transformed by Matrix, does not intersect Clip
### Example
#### Example Output
~~~~
quickReject true
quickReject false
~~~~
### See Also
getLocalClipBounds[2] getTotalMatrix SkBitmap::drawsNothing
---
## getLocalClipBounds
SkRect getLocalClipBounds() const
Return bounds of Clip, transformed by inverse of Matrix. If Clip is empty,
return SkRect::MakeEmpty, where all Rect sides equal zero.
Rect returned is outset by one to account for partial pixel coverage if Clip
is Anti-aliased.
### Return Value
bounds of Clip in local coordinates
### Example
Initial bounds is device bounds outset by 1 on all sides.
Clipped bounds is
clipPath bounds outset by 1 on all sides.
Scaling the canvas by two in x and y scales the local bounds by 1/2 in x and y.
#### Example Output
~~~~
left:-1 top:-1 right:257 bottom:257
left:29 top:129 right:121 bottom:231
left:14.5 top:64.5 right:60.5 bottom:115.5
~~~~
### See Also
getDeviceClipBounds[2] getBaseLayerSize quickReject[2]
---
bool getLocalClipBounds(SkRect* bounds) const
Return bounds of Clip, transformed by inverse of Matrix. If Clip is empty,
return false, and set bounds to SkRect::MakeEmpty, where all Rect sides equal zero.
bounds is outset by one to account for partial pixel coverage if Clip
is Anti-aliased.
### Parameters
### Return Value
true if Clip bounds is not empty
### Example
#### Example Output
~~~~
local bounds empty = false
local bounds empty = true
~~~~
### See Also
getDeviceClipBounds[2] getBaseLayerSize quickReject[2]
---
## getDeviceClipBounds
SkIRect getDeviceClipBounds() const
Return IRect bounds of Clip, unaffected by Matrix. If Clip is empty,
return SkRect::MakeEmpty, where all Rect sides equal zero.
Unlike getLocalClipBounds, returned IRect is not outset.
### Return Value
bounds of Clip in Device coordinates
### Example
Initial bounds is device bounds, not outset.
Clipped bounds is
clipPath bounds, not outset.
Scaling the canvas by 1/2 in x and y scales the device bounds by 1/2 in x and y.
#### Example Output
~~~~
left:0 top:0 right:256 bottom:256
left:30 top:130 right:120 bottom:230
left:15 top:65 right:60 bottom:115
~~~~
### See Also
getLocalClipBounds[2] getBaseLayerSize quickReject[2]
---
bool getDeviceClipBounds(SkIRect* bounds) const
Return IRect bounds of Clip, unaffected by Matrix. If Clip is empty,
return false, and set bounds to SkRect::MakeEmpty, where all Rect sides equal zero.
Unlike getLocalClipBounds, bounds is not outset.
### Parameters
### Return Value
true if Clip bounds is not empty
### Example
#### Example Output
~~~~
device bounds empty = false
device bounds empty = true
~~~~
### See Also
getLocalClipBounds[2] getBaseLayerSize quickReject[2]
---
## Draw
| name | description |
| --- | --- |
| clear | fills Clip with Color |
| drawAnnotation | associates a Rect with a key-value pair |
| | drawAnnotation(const SkRect& rect, const char key[], SkData* value) |
| | drawAnnotation(const SkRect& rect, const char key[], const sk sp<SkData>& value) |
| drawArc | draws Arc using Clip, Matrix, and Paint |
| drawAtlas | draws sprites using Clip, Matrix, and Paint |
| | drawAtlas(const SkImage* atlas, const SkRSXform xform[], const SkRect tex[], const SkColor colors[], int count, SkBlendMode mode, const SkRect* cullRect, const SkPaint* paint) |
| | drawAtlas(const sk sp<SkImage>& atlas, const SkRSXform xform[], const SkRect tex[], const SkColor colors[], int count, SkBlendMode mode, const SkRect* cullRect, const SkPaint* paint) |
| | drawAtlas(const SkImage* atlas, const SkRSXform xform[], const SkRect tex[], int count, const SkRect* cullRect, const SkPaint* paint) |
| | drawAtlas(const sk sp<SkImage>& atlas, const SkRSXform xform[], const SkRect tex[], int count, const SkRect* cullRect, const SkPaint* paint) |
| drawCircle | draws Circle using Clip, Matrix, and Paint |
| | drawCircle(SkScalar cx, SkScalar cy, SkScalar radius, const SkPaint& paint) |
| | drawCircle(SkPoint center, SkScalar radius, const SkPaint& paint) |
| drawColor | fills Clip with Color and Blend Mode |
| drawDRRect | draws double Round Rect stroked or filled |
| drawDrawable | draws Drawable, encapsulated drawing commands |
| | drawDrawable(SkDrawable* drawable, const SkMatrix* matrix = nullptr) |
| | drawDrawable(SkDrawable* drawable, SkScalar x, SkScalar y) |
| drawIRect | draws IRect using Clip, Matrix, and Paint |
| drawLine | draws line segment between two points |
| | drawLine(SkScalar x0, SkScalar y0, SkScalar x1, SkScalar y1, const SkPaint& paint) |
| | drawLine(SkPoint p0, SkPoint p1, const SkPaint& paint) |
| drawOval | draws Oval using Clip, Matrix, and Paint |
| drawPaint | fills Clip with Paint |
| drawPatch | draws Coons_Patch |
| | drawPatch(const SkPoint cubics[12], const SkColor colors[4], const SkPoint texCoords[4], SkBlendMode mode, const SkPaint& paint) |
| | drawPatch(const SkPoint cubics[12], const SkColor colors[4], const SkPoint texCoords[4], const SkPaint& paint) |
| drawPath | draws Path using Clip, Matrix, and Paint |
| drawPicture | draws Picture using Clip and Matrix |
| | drawPicture(const SkPicture* picture) |
| | drawPicture(const sk sp<SkPicture>& picture) |
| | drawPicture(const SkPicture* picture, const SkMatrix* matrix, const SkPaint* paint) |
| | drawPicture(const sk sp<SkPicture>& picture, const SkMatrix* matrix, const SkPaint* paint) |
| drawPoint | draws point at (x, y) position |
| | drawPoint(SkScalar x, SkScalar y, const SkPaint& paint) |
| | drawPoint(SkPoint p, const SkPaint& paint) |
| drawPoints | draws array as points, lines, polygon |
| drawRRect | draws Round Rect using Clip, Matrix, and Paint |
| drawRect | draws Rect using Clip, Matrix, and Paint |
| drawRegion | draws Region using Clip, Matrix, and Paint |
| drawRoundRect | draws Round Rect using Clip, Matrix, and Paint |
| drawVertices | draws Vertices, a triangle mesh |
| | drawVertices(const SkVertices* vertices, SkBlendMode mode, const SkPaint& paint) |
| | drawVertices(const sk sp<SkVertices>& vertices, SkBlendMode mode, const SkPaint& paint) |
## drawColor
void drawColor(SkColor color, SkBlendMode mode = SkBlendMode::kSrcOver)
Fill Clip with Color color.
mode determines how Color ARGB is combined with destination.
### Parameters
### Example
### See Also
clear SkBitmap::erase drawPaint
---
## clear
void clear(SkColor color)
Fill Clip with Color color using SkBlendMode::kSrc.
This has the effect of replacing all pixels contained by Clip with color.
### Parameters
### Example
### See Also
drawColor SkBitmap::erase drawPaint
---
## discard
void discard()
Make Canvas contents undefined. Subsequent calls that read Canvas pixels,
such as drawing with SkBlendMode, return undefined results. discard does
not change Clip or Matrix.
discard may do nothing, depending on the implementation of Surface or Device
that created Canvas.
discard allows optimized performance on subsequent draws by removing
cached data associated with Surface or Device.
It is not necessary to call discard once done with Canvas;
any cached data is deleted when owning Surface or Device is deleted.
### See Also
flush SkSurface::prepareForExternalIO GrContext::abandonContext
---
## drawPaint
void drawPaint(const SkPaint& paint)
Fill Clip with Paint paint. Paint components Mask Filter, Shader,
Color Filter, Image Filter, and Blend Mode affect drawing;
Path Effect in paint is ignored.
### Parameters
### Example
### See Also
clear drawColor SkBitmap::erase
---
## Enum SkCanvas::PointMode
enum PointMode {
kPoints PointMode,
kLines PointMode,
kPolygon PointMode,
};
Selects if an array of points are drawn as discrete points, as lines, or as
an open polygon.
### Constants
### Example
The upper left corner shows three squares when drawn as points.
The upper right corner shows one line; when drawn as lines, two points are required per line.
The lower right corner shows two lines; when draw as polygon, no miter is drawn at the corner.
The lower left corner shows two lines with a miter when path contains polygon.
### See Also
drawLine[2] drawPoint[2] drawPath
## drawPoints
void drawPoints(PointMode mode, size_t count, const SkPoint pts[], const SkPaint& paint)
Draw pts using Clip, Matrix and Paint paint.
count is the number of points; if count is less than one, has no effect.
mode may be one of: kPoints PointMode, kLines PointMode, or kPolygon PointMode.
If mode is kPoints PointMode, the shape of point drawn depends on paint
Paint Stroke Cap. If paint is set to SkPaint::kRound Cap, each point draws a
circle of diameter Paint Stroke Width. If paint is set to SkPaint::kSquare Cap
or SkPaint::kButt Cap, each point draws a square of width and height
Paint Stroke Width.
If mode is kLines PointMode, each pair of points draws a line segment.
One line is drawn for every two points; each point is used once. If count is odd,
the final point is ignored.
If mode is kPolygon PointMode, each adjacent pair of points draws a line segment.
count minus one lines are drawn; the first and last point are used once.
Each line segment respects paint Paint Stroke Cap and Paint Stroke Width.
Paint Style is ignored, as if were set to SkPaint::kStroke Style.
Always draws each element one at a time; is not affected by
Paint Stroke Join, and unlike drawPath, does not create a mask from all points
and lines before drawing.
### Parameters
mode |
whether pts draws points or lines |
count |
number of points in the array |
pts |
array of points to draw |
paint |
stroke, blend, color, and so on, used to draw |
### Example
The first column draws points. |
The second column draws points as lines. |
The third column draws points as a polygon. |
The fourth column draws points as a polygonal path. |
The first row uses a round cap and round join. |
The second row uses a square cap and a miter join. |
The third row uses a butt cap and a bevel join. |
The transparent color makes multiple line draws visible;
the path is drawn all at once.
### See Also
drawLine[2] drawPoint[2] drawPath
---
## drawPoint
void drawPoint(SkScalar x, SkScalar y, const SkPaint& paint)
Draw point at (x, y) using Clip, Matrix and Paint paint.
The shape of point drawn depends on paint Paint Stroke Cap.
If paint is set to SkPaint::kRound Cap, draw a circle of diameter
Paint Stroke Width. If paint is set to SkPaint::kSquare Cap or SkPaint::kButt Cap,
draw a square of width and height Paint Stroke Width.
Paint Style is ignored, as if were set to SkPaint::kStroke Style.
### Parameters
x |
left edge of circle or square |
y |
top edge of circle or square |
paint |
stroke, blend, color, and so on, used to draw |
### Example
### See Also
drawPoints drawCircle[2] drawRect drawLine[2] drawPath
---
void drawPoint(SkPoint p, const SkPaint& paint)
Draw point p using Clip, Matrix and Paint paint.
The shape of point drawn depends on paint Paint Stroke Cap.
If paint is set to SkPaint::kRound Cap, draw a circle of diameter
Paint Stroke Width. If paint is set to SkPaint::kSquare Cap or SkPaint::kButt Cap,
draw a square of width and height Paint Stroke Width.
Paint Style is ignored, as if were set to SkPaint::kStroke Style.
### Parameters
p |
top-left edge of circle or square |
paint |
stroke, blend, color, and so on, used to draw |
### Example
### See Also
drawPoints drawCircle[2] drawRect drawLine[2] drawPath
---
## drawLine
void drawLine(SkScalar x0, SkScalar y0, SkScalar x1, SkScalar y1, const SkPaint& paint)
Draws line segment from (x0, y0) to (x1, y1) using Clip, Matrix, and Paint paint.
In paint: Paint Stroke Width describes the line thickness;
Paint Stroke Cap draws the end rounded or square;
Paint Style is ignored, as if were set to SkPaint::kStroke Style.
### Parameters
x0 |
start of line segment on x-axis |
y0 |
start of line segment on y-axis |
x1 |
end of line segment on x-axis |
y1 |
end of line segment on y-axis |
paint |
stroke, blend, color, and so on, used to draw |
### Example
### See Also
drawPoint[2] drawCircle[2] drawRect drawPath
---
void drawLine(SkPoint p0, SkPoint p1, const SkPaint& paint)
Draws line segment from p0 to p1 using Clip, Matrix, and Paint paint.
In paint: Paint Stroke Width describes the line thickness;
Paint Stroke Cap draws the end rounded or square;
Paint Style is ignored, as if were set to SkPaint::kStroke Style.
### Parameters
p0 |
start of line segment |
p1 |
end of line segment |
paint |
stroke, blend, color, and so on, used to draw |
### Example
### See Also
drawPoint[2] drawCircle[2] drawRect drawPath
---
## drawRect
void drawRect(const SkRect& rect, const SkPaint& paint)
Draw Rect rect using Clip, Matrix, and Paint paint.
In paint: Paint Style determines if rectangle is stroked or filled;
if stroked, Paint Stroke Width describes the line thickness, and
Paint Stroke Join draws the corners rounded or square.
### Parameters
rect |
rectangle to draw |
paint |
stroke or fill, blend, color, and so on, used to draw |
### Example
### See Also
drawIRect drawRRect drawRoundRect drawRegion drawPath drawLine[2]
---
## drawIRect
void drawIRect(const SkIRect& rect, const SkPaint& paint)
Draw IRect rect using Clip, Matrix, and Paint paint.
In paint: Paint Style determines if rectangle is stroked or filled;
if stroked, Paint Stroke Width describes the line thickness, and
Paint Stroke Join draws the corners rounded or square.
### Parameters
rect |
rectangle to draw |
paint |
stroke or fill, blend, color, and so on, used to draw |
### Example
### See Also
drawRect drawRRect drawRoundRect drawRegion drawPath drawLine[2]
---
## drawRegion
void drawRegion(const SkRegion& region, const SkPaint& paint)
Draw Region region using Clip, Matrix, and Paint paint.
In paint: Paint Style determines if rectangle is stroked or filled;
if stroked, Paint Stroke Width describes the line thickness, and
Paint Stroke Join draws the corners rounded or square.
### Parameters
### Example
### See Also
drawRect drawIRect drawPath
---
## drawOval
void drawOval(const SkRect& oval, const SkPaint& paint)
Draw Oval oval using Clip, Matrix, and Paint.
In paint: Paint Style determines if Oval is stroked or filled;
if stroked, Paint Stroke Width describes the line thickness.
### Parameters
### Example
### See Also
drawCircle[2] drawPoint[2] drawPath drawRRect drawRoundRect
---
## drawRRect
void drawRRect(const SkRRect& rrect, const SkPaint& paint)
Draw Round Rect rrect using Clip, Matrix, and Paint paint.
In paint: Paint Style determines if rrect is stroked or filled;
if stroked, Paint Stroke Width describes the line thickness.
rrect may represent a rectangle, circle, oval, uniformly rounded rectangle, or
may have any combination of positive non-square radii for the four corners.
### Parameters
### Example
### See Also
drawRect drawRoundRect drawDRRect drawCircle[2] drawOval drawPath
---
## drawDRRect
void drawDRRect(const SkRRect& outer, const SkRRect& inner, const SkPaint& paint)
Draw Round Rect outer and inner
using Clip, Matrix, and Paint paint.
outer must contain inner or the drawing is undefined.
In paint: Paint Style determines if Round Rect is stroked or filled;
if stroked, Paint Stroke Width describes the line thickness.
If stroked and Round Rect corner has zero length radii, Paint Stroke Join can
draw corners rounded or square.
GPU-backed platforms optimize drawing when both outer and inner are
concave and outer contains inner. These platforms may not be able to draw
Path built with identical data as fast.
### Parameters
### Example
### Example
Outer
Rect has no corner radii, but stroke join is rounded.
Inner
Round Rect has corner radii; outset stroke increases radii of corners.
Stroke join does not affect
inner Round Rect since it has no sharp corners.
### See Also
drawRect drawRoundRect drawRRect drawCircle[2] drawOval drawPath
---
## drawCircle
void drawCircle(SkScalar cx, SkScalar cy, SkScalar radius, const SkPaint& paint)
Draw Circle at (cx, cy) with radius using Clip, Matrix, and Paint paint.
If radius is zero or less, nothing is drawn.
In paint: Paint Style determines if Circle is stroked or filled;
if stroked, Paint Stroke Width describes the line thickness.
### Parameters
### Example
### See Also
drawOval drawRRect drawRoundRect drawPath drawArc drawPoint[2] drawLine[2]
---
void drawCircle(SkPoint center, SkScalar radius, const SkPaint& paint)
Draw Circle at center with radius using Clip, Matrix, and Paint paint.
If radius is zero or less, nothing is drawn.
In paint: Paint Style determines if Circle is stroked or filled;
if stroked, Paint Stroke Width describes the line thickness.
### Parameters
### Example
### See Also
drawOval drawRRect drawRoundRect drawPath drawArc drawPoint[2] drawLine[2]
---
## drawArc
void drawArc(const SkRect& oval, SkScalar startAngle, SkScalar sweepAngle, bool useCenter,
const SkPaint& paint)
Draw Arc using Clip, Matrix, and Paint paint.
Arc is part of Oval bounded by oval, sweeping from startAngle to startAngle plus
sweepAngle. startAngle and sweepAngle are in degrees.
startAngle of zero places start point at the right middle edge of oval.
A positive sweepAngle places Arc end point clockwise from start point;
a negative sweepAngle places Arc end point counterclockwise from start point.
sweepAngle may exceed 360 degrees, a full circle.
If useCenter is true, draw a wedge that includes lines from oval
center to Arc end points. If useCenter is false, draw Arc between end points.
If Rect oval is empty or sweepAngle is zero, nothing is drawn.
### Parameters
### Example
### Example
### See Also
SkPath::arcTo[2][3][4][5] drawCircle[2] drawOval drawPath
---
## drawRoundRect
void drawRoundRect(const SkRect& rect, SkScalar rx, SkScalar ry, const SkPaint& paint)
Draw Round Rect bounded by Rect rect, with corner radii (rx, ry) using Clip,
Matrix, and Paint paint.
In paint: Paint Style determines if Round Rect is stroked or filled;
if stroked, Paint Stroke Width describes the line thickness.
If rx or ry are less than zero, they are treated as if they are zero.
If rx plus ry exceeds rect width or rect height, radii are scaled down to fit.
If rx and ry are zero, Round Rect is drawn as Rect and if stroked is affected by
Paint Stroke Join.
### Parameters
rect |
Rect bounds of Round Rect to draw |
rx |
axis length in x of oval describing rounded corners |
ry |
axis length in y of oval describing rounded corners |
paint |
stroke, blend, color, and so on, used to draw |
### Example
Top row has a zero radius a generates a rectangle.
Second row radii sum to less than sides.
Third row radii sum equals sides.
Fourth row radii sum exceeds sides; radii are scaled to fit.
### See Also
DrawRRect drawRect drawDRRect drawPath drawCircle[2] drawOval drawPoint[2]
---
## drawPath
void drawPath(const SkPath& path, const SkPaint& paint)
Draw Path path using Clip, Matrix, and Paint paint.
Path contains an array of Path Contour, each of which may be open or closed.
In paint: Paint Style determines if Round Rect is stroked or filled:
if filled, Path Fill Type determines whether Path Contour describes inside or
outside of fill; if stroked, Paint Stroke Width describes the line thickness,
Paint Stroke Cap describes line ends, and Paint Stroke Join describes how
corners are drawn.
### Parameters
path |
Path to draw |
paint |
stroke, blend, color, and so on, used to draw |
### Example
Top rows draw stroked
path with combinations of joins and caps. The open contour
is affected by caps; the closed contour is affected by joins.
Bottom row draws fill the same for open and closed contour.
First bottom column shows winding fills overlap.
Second bottom column shows even odd fills exclude overlap.
Third bottom column shows inverse winding fills area outside both contours.
### See Also
SkPath drawLine[2] drawArc drawRect drawPoints
---
## Draw Image
drawImage, drawImageRect, and drawImageNine can be called with a bare pointer or
a smart pointer as a convenience. The pairs of calls are otherwise identical.
## drawImage
void drawImage(const SkImage* image, SkScalar left, SkScalar top, const SkPaint* paint = nullptr)
Draw Image image, with its top-left corner at (left, top),
using Clip, Matrix, and optional Paint paint.
If paint is supplied, apply Color Filter, Color Alpha, Image Filter, Blend Mode,
and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds. If generated
mask extends beyond image bounds, replicate image edge colors, just as Shader
made from SkImage::makeShader with SkShader::kClamp TileMode set replicates the
image edge color when it samples outside of its bounds.
### Parameters
### Example
### See Also
drawBitmap drawImageLattice drawImageNine[2] drawImageRect[2][3][4][5][6] SkPaint::setImageFilter
---
void drawImage(const sk_sp<SkImage>& image, SkScalar left, SkScalar top,
const SkPaint* paint = nullptr)
Draw Image image, with its top-left corner at (left, top),
using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds. If generated
mask extends beyond image bounds, replicate image edge colors, just as Shader
made from SkImage::makeShader with SkShader::kClamp TileMode set replicates the
image edge color when it samples outside of its bounds.
### Parameters
### Example
### See Also
drawBitmap drawImageLattice drawImageNine[2] drawImageRect[2][3][4][5][6] SkPaint::setImageFilter
---
## Enum SkCanvas::SrcRectConstraint
enum SrcRectConstraint {
kStrict SrcRectConstraint,
kFast SrcRectConstraint,
};
SrcRectConstraint controls the behavior at the edge of source Rect,
provided to drawImageRect, trading off speed for precision.
Image Filter in Paint may sample multiple pixels in the image. Source Rect
restricts the bounds of pixels that may be read. Image Filter may slow down if
it cannot read outside the bounds, when sampling near the edge of source Rect.
SrcRectConstraint specifies whether an Image Filter is allowed to read pixels
outside source Rect.
### Constants
### Example
redBorder contains a black and white checkerboard bordered by red.
redBorder is drawn scaled by 16 on the left.
The middle and right bitmaps are filtered checkerboards.
Drawing the checkerboard with
kStrict SrcRectConstraint shows only a blur of black and white.
Drawing the checkerboard with
kFast SrcRectConstraint allows red to bleed in the corners.
### See Also
drawImageRect[2][3][4][5][6] drawImage[2] SkPaint::setImageFilter
## drawImageRect
void drawImageRect(const SkImage* image, const SkRect& src, const SkRect& dst, const SkPaint* paint,
SrcRectConstraint constraint = kStrict_SrcRectConstraint)
Draw Rect src of Image image, scaled and translated to fill Rect dst.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds.
If generated mask extends beyond image bounds, replicate image edge colors, just
as Shader made from SkImage::makeShader with SkShader::kClamp TileMode set
replicates the image edge color when it samples outside of its bounds.
constraint set to kStrict SrcRectConstraint limits Paint Filter Quality to
sample within src; set to kFast SrcRectConstraint allows sampling outside to
improve performance.
### Parameters
### Example
### See Also
SrcRectConstraint drawImage[2] drawImageLattice drawImageNine[2]
---
void drawImageRect(const SkImage* image, const SkIRect& isrc, const SkRect& dst, const SkPaint* paint,
SrcRectConstraint constraint = kStrict_SrcRectConstraint)
Draw IRect isrc of Image image, scaled and translated to fill Rect dst.
Note that isrc is on integer pixel boundaries; dst may include fractional
boundaries. Additionally transform draw using Clip, Matrix, and optional Paint
paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds.
If generated mask extends beyond image bounds, replicate image edge colors, just
as Shader made from SkImage::makeShader with SkShader::kClamp TileMode set
replicates the image edge color when it samples outside of its bounds.
constraint set to kStrict SrcRectConstraint limits Paint Filter Quality to
sample within isrc; set to kFast SrcRectConstraint allows sampling outside to
improve performance.
### Parameters
### Example
### See Also
SrcRectConstraint drawImage[2] drawImageLattice drawImageNine[2]
---
void drawImageRect(const SkImage* image, const SkRect& dst, const SkPaint* paint,
SrcRectConstraint constraint = kStrict_SrcRectConstraint)
Draw Image image, scaled and translated to fill Rect dst, using Clip, Matrix,
and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds.
If generated mask extends beyond image bounds, replicate image edge colors, just
as Shader made from SkImage::makeShader with SkShader::kClamp TileMode set
replicates the image edge color when it samples outside of its bounds.
constraint set to kStrict SrcRectConstraint limits Paint Filter Quality to
sample within image; set to kFast SrcRectConstraint allows sampling outside to
improve performance.
### Parameters
### Example
### See Also
SrcRectConstraint drawImage[2] drawImageLattice drawImageNine[2]
---
void drawImageRect(const sk_sp<SkImage>& image, const SkRect& src, const SkRect& dst,
const SkPaint* paint, SrcRectConstraint constraint = kStrict_SrcRectConstraint)
Draw Rect src of Image image, scaled and translated to fill Rect dst.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds.
If generated mask extends beyond image bounds, replicate image edge colors, just
as Shader made from SkImage::makeShader with SkShader::kClamp TileMode set
replicates the image edge color when it samples outside of its bounds.
constraint set to kStrict SrcRectConstraint limits Paint Filter Quality to
sample within src; set to kFast SrcRectConstraint allows sampling outside to
improve performance.
### Parameters
### Example
Canvas scales and translates; transformation from
src to
dst also scales.
The two matrices are concatenated to create the final transformation.
### See Also
SrcRectConstraint drawImage[2] drawImageLattice drawImageNine[2]
---
void drawImageRect(const sk_sp<SkImage>& image, const SkIRect& isrc, const SkRect& dst,
const SkPaint* paint, SrcRectConstraint constraint = kStrict_SrcRectConstraint)
Draw IRect isrc of Image image, scaled and translated to fill Rect dst.
isrc is on integer pixel boundaries; dst may include fractional boundaries.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds.
If generated mask extends beyond image bounds, replicate image edge colors, just
as Shader made from SkImage::makeShader with SkShader::kClamp TileMode set
replicates the image edge color when it samples outside of its bounds.
constraint set to kStrict SrcRectConstraint limits Paint Filter Quality to
sample within image; set to kFast SrcRectConstraint allows sampling outside to
improve performance.
### Parameters
### Example
### See Also
SrcRectConstraint drawImage[2] drawImageLattice drawImageNine[2]
---
void drawImageRect(const sk_sp<SkImage>& image, const SkRect& dst, const SkPaint* paint,
SrcRectConstraint constraint = kStrict_SrcRectConstraint)
Draw Image image, scaled and translated to fill Rect dst,
using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds.
If generated mask extends beyond image bounds, replicate image edge colors, just
as Shader made from SkImage::makeShader with SkShader::kClamp TileMode set
replicates the image edge color when it samples outside of its bounds.
constraint set to kStrict SrcRectConstraint limits Paint Filter Quality to
sample within image; set to kFast SrcRectConstraint allows sampling outside to
improve performance.
### Parameters
### Example
### See Also
SrcRectConstraint drawImage[2] drawImageLattice drawImageNine[2]
---
## drawImageNine
void drawImageNine(const SkImage* image, const SkIRect& center, const SkRect& dst,
const SkPaint* paint = nullptr)
Draw Image image stretched proportionally to fit into Rect dst.
IRect center divides the image into nine sections: four sides, four corners, and
the center. Corners are unmodified or scaled down proportionately if their sides
are larger than dst; center and four sides are scaled to fit remaining space, if any.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds.
If generated mask extends beyond image bounds, replicate image edge colors, just
as Shader made from SkImage::makeShader with SkShader::kClamp TileMode set
replicates the image edge color when it samples outside of its bounds.
### Parameters
### Example
The leftmost
image is smaller than
center; only corners are drawn, all scaled to fit.
The second
image equals the size of
center; only corners are drawn without scaling.
The remaining images are larger than
center. All corners draw without scaling.
The sides and
center are scaled if needed to take up the remaining space.
### See Also
drawImage[2] drawBitmapNine drawImageLattice drawImageRect[2][3][4][5][6]
---
void drawImageNine(const sk_sp<SkImage>& image, const SkIRect& center, const SkRect& dst,
const SkPaint* paint = nullptr)
Draw Image image stretched proportionally to fit into Rect dst.
IRect center divides the image into nine sections: four sides, four corners, and
the center. Corners are not scaled, or scaled down proportionately if their sides
are larger than dst; center and four sides are scaled to fit remaining space, if any.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If image is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from image bounds.
If generated mask extends beyond image bounds, replicate image edge colors, just
as Shader made from SkImage::makeShader with SkShader::kClamp TileMode set
replicates the image edge color when it samples outside of its bounds.
### Parameters
### Example
The two leftmost images has four corners and sides to the left and right of
center.
The leftmost
image scales the width of corners proportionately to fit.
The third and fourth
image corners are not scaled; the sides and
center are scaled to
fill the remaining space.
The rightmost
image has four corners scaled vertically to fit, and uses sides above
and below
center to fill the remaining space.
### See Also
drawImage[2] drawBitmapNine drawImageLattice drawImageRect[2][3][4][5][6]
---
## drawBitmap
void drawBitmap(const SkBitmap& bitmap, SkScalar left, SkScalar top, const SkPaint* paint = nullptr)
Draw Bitmap bitmap, with its top-left corner at (left, top),
using Clip, Matrix, and optional Paint paint.
If Paint paint is not nullptr, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If bitmap is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from bitmap bounds.
If generated mask extends beyond bitmap bounds, replicate bitmap edge colors,
just as Shader made from SkShader::MakeBitmapShader with
SkShader::kClamp TileMode set replicates the bitmap edge color when it samples
outside of its bounds.
### Parameters
### Example
### See Also
drawImage[2] drawBitmapLattice drawBitmapNine drawBitmapRect[2][3] SkBitmap::readPixels[2][3][4] SkBitmap::writePixels[2][3]
---
## drawBitmapRect
void drawBitmapRect(const SkBitmap& bitmap, const SkRect& src, const SkRect& dst,
const SkPaint* paint, SrcRectConstraint constraint = kStrict_SrcRectConstraint)
Draw Rect src of Bitmap bitmap, scaled and translated to fill Rect dst.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If bitmap is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from bitmap bounds.
If generated mask extends beyond bitmap bounds, replicate bitmap edge colors,
just as Shader made from SkShader::MakeBitmapShader with
SkShader::kClamp TileMode set replicates the bitmap edge color when it samples
outside of its bounds.
constraint set to kStrict SrcRectConstraint limits Paint Filter Quality to
sample within src; set to kFast SrcRectConstraint allows sampling outside to
improve performance.
### Parameters
### Example
### See Also
drawImageRect[2][3][4][5][6] drawBitmap drawBitmapLattice drawBitmapNine
---
void drawBitmapRect(const SkBitmap& bitmap, const SkIRect& isrc, const SkRect& dst,
const SkPaint* paint, SrcRectConstraint constraint = kStrict_SrcRectConstraint)
Draw IRect isrc of Bitmap bitmap, scaled and translated to fill Rect dst.
isrc is on integer pixel boundaries; dst may include fractional boundaries.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If bitmap is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from bitmap bounds.
If generated mask extends beyond bitmap bounds, replicate bitmap edge colors,
just as Shader made from SkShader::MakeBitmapShader with
SkShader::kClamp TileMode set replicates the bitmap edge color when it samples
outside of its bounds.
constraint set to kStrict SrcRectConstraint limits Paint Filter Quality to
sample within isrc; set to kFast SrcRectConstraint allows sampling outside to
improve performance.
### Parameters
### Example
### See Also
drawImageRect[2][3][4][5][6] drawBitmap drawBitmapLattice drawBitmapNine
---
void drawBitmapRect(const SkBitmap& bitmap, const SkRect& dst, const SkPaint* paint,
SrcRectConstraint constraint = kStrict_SrcRectConstraint)
Draw Bitmap bitmap, scaled and translated to fill Rect dst.
bitmap bounds is on integer pixel boundaries; dst may include fractional boundaries.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If bitmap is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from bitmap bounds.
If generated mask extends beyond bitmap bounds, replicate bitmap edge colors,
just as Shader made from SkShader::MakeBitmapShader with
SkShader::kClamp TileMode set replicates the bitmap edge color when it samples
outside of its bounds.
constraint set to kStrict SrcRectConstraint limits Paint Filter Quality to
sample within bitmap; set to kFast SrcRectConstraint allows sampling outside to
improve performance.
### Parameters
### Example
### See Also
drawImageRect[2][3][4][5][6] drawBitmap drawBitmapLattice drawBitmapNine
---
## drawBitmapNine
void drawBitmapNine(const SkBitmap& bitmap, const SkIRect& center, const SkRect& dst,
const SkPaint* paint = nullptr)
Draw Bitmap bitmap stretched proportionally to fit into Rect dst.
IRect center divides the bitmap into nine sections: four sides, four corners,
and the center. Corners are not scaled, or scaled down proportionately if their
sides are larger than dst; center and four sides are scaled to fit remaining
space, if any.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If bitmap is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from bitmap bounds.
If generated mask extends beyond bitmap bounds, replicate bitmap edge colors,
just as Shader made from SkShader::MakeBitmapShader with
SkShader::kClamp TileMode set replicates the bitmap edge color when it samples
outside of its bounds.
### Parameters
### Example
The two leftmost
bitmap draws has four corners and sides to the left and right of
center.
The leftmost
bitmap draw scales the width of corners proportionately to fit.
The third and fourth draw corners are not scaled; the sides and
center are scaled to
fill the remaining space.
The rightmost
bitmap draw has four corners scaled vertically to fit, and uses sides above
and below
center to fill the remaining space.
### See Also
drawImageNine[2] drawBitmap drawBitmapLattice drawBitmapRect[2][3]
---
# Struct SkCanvas::Lattice
struct Lattice {
enum RectType ...
const int* fXDivs;
const int* fYDivs;
const RectType* fRectTypes;
int fXCount;
int fYCount;
const SkIRect* fBounds;
const SkColor* fColors;
};
Lattice divides Bitmap or Image into a rectangular grid.
Grid entries on even columns and even rows are fixed; these entries are
always drawn at their original size if the destination is large enough.
If the destination side is too small to hold the fixed entries, all fixed
entries are proportionately scaled down to fit.
The grid entries not on even columns and rows are scaled to fit the
remaining space, if any.
## Enum SkCanvas::Lattice::RectType
enum RectType : uint8_t {
kDefault = 0,
kTransparent,
kFixedColor,
};
Optional setting per rectangular grid entry to make it transparent,
or to fill the grid entry with a color.
### Constants
const int* fXDivs
Array of x-coordinates that divide the bitmap vertically.
Array entries must be unique, increasing, greater than or equal to
fBounds left edge, and less than fBounds right edge.
Set the first element to fBounds left to collapse the left column of
fixed grid entries.
const int* fYDivs
Array of y-coordinates that divide the bitmap horizontally.
Array entries must be unique, increasing, greater than or equal to
fBounds top edge, and less than fBounds bottom edge.
Set the first element to fBounds top to collapse the top row of fixed
grid entries.
const RectType* fRectTypes
Optional array of fill types, one per rectangular grid entry:
array length must be( fXCount + 1) * (fYCount + 1).
Each RectType is one of: kDefault, kTransparent, kFixedColor.
Array entries correspond to the rectangular grid entries, ascending
left to right and then top to bottom.
int fXCount
Number of entries in fXDivs array; one less than the number of
horizontal divisions.
int fYCount
Number of entries in fYDivs array; one less than the number of vertical
divisions.
const SkIRect* fBounds
Optional subset IRect source to draw from.
If nullptr, source bounds is dimensions of Bitmap or Image.
const SkColor* fColors
Optional array of colors, one per rectangular grid entry.
Array length must be( fXCount + 1) * (fYCount + 1).
Array entries correspond to the rectangular grid entries, ascending
left to right, then top to bottom.
## drawBitmapLattice
void drawBitmapLattice(const SkBitmap& bitmap, const Lattice& lattice, const SkRect& dst,
const SkPaint* paint = nullptr)
Draw Bitmap bitmap stretched proportionally to fit into Rect dst.
Lattice lattice divides bitmap into a rectangular grid.
Each intersection of an even-numbered row and column is fixed; like the corners
of drawBitmapNine, fixed lattice elements never scale larger than their initial
size and shrink proportionately when all fixed elements exceed the bitmap
dimension. All other grid elements scale to fill the available space, if any.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If bitmap is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from bitmap bounds.
If generated mask extends beyond bitmap bounds, replicate bitmap edge colors,
just as Shader made from SkShader::MakeBitmapShader with
SkShader::kClamp TileMode set replicates the bitmap edge color when it samples
outside of its bounds.
### Parameters
### Example
The two leftmost
bitmap draws has four corners and sides to the left and right of center.
The leftmost
bitmap draw scales the width of corners proportionately to fit.
The third and fourth draw corners are not scaled; the sides are scaled to
fill the remaining space; the center is transparent.
The rightmost
bitmap draw has four corners scaled vertically to fit, and uses sides above
and below center to fill the remaining space.
### See Also
drawImageLattice drawBitmap drawBitmapNine Lattice
---
## drawImageLattice
void drawImageLattice(const SkImage* image, const Lattice& lattice, const SkRect& dst,
const SkPaint* paint = nullptr)
Draw Image image stretched proportionally to fit into Rect dst.
Lattice lattice divides image into a rectangular grid.
Each intersection of an even-numbered row and column is fixed; like the corners
of drawBitmapNine, fixed lattice elements never scale larger than their initial
size and shrink proportionately when all fixed elements exceed the bitmap
dimension. All other grid elements scale to fill the available space, if any.
Additionally transform draw using Clip, Matrix, and optional Paint paint.
If Paint paint is supplied, apply Color Filter, Color Alpha, Image Filter,
Blend Mode, and Draw Looper. If bitmap is kAlpha 8 SkColorType, apply Shader.
If paint contains Mask Filter, generate mask from bitmap bounds.
If generated mask extends beyond bitmap bounds, replicate bitmap edge colors,
just as Shader made from SkShader::MakeBitmapShader with
SkShader::kClamp TileMode set replicates the bitmap edge color when it samples
outside of its bounds.
### Parameters
### Example
The leftmost
image is smaller than center; only corners are drawn, all scaled to fit.
The second
image equals the size of center; only corners are drawn without scaling.
The remaining images are larger than center. All corners draw without scaling. The sides
are scaled if needed to take up the remaining space; the center is transparent.
### See Also
drawBitmapLattice drawImage[2] drawImageNine[2] Lattice
---
## Draw Text
| name | description |
| --- | --- |
| drawPosText | draws text at array of (x, y) positions |
| drawPosTextH | draws text at x positions with common baseline |
| drawString | draws null terminated string at (x, y) using font advance |
| | drawString(const char* string, SkScalar x, SkScalar y, const SkPaint& paint) |
| | drawString(const SkString& string, SkScalar x, SkScalar y, const SkPaint& paint) |
| drawText | draws text at (x, y), using font advance |
| drawTextBlob | draws text with arrays of positions and Paint |
| | drawTextBlob(const SkTextBlob* blob, SkScalar x, SkScalar y, const SkPaint& paint) |
| | drawTextBlob(const sk sp<SkTextBlob>& blob, SkScalar x, SkScalar y, const SkPaint& paint) |
| drawTextOnPath | draws text following Path contour |
| drawTextOnPathHV | draws text following Path with offsets |
| drawTextRSXform | draws text with array of RSXform |
## drawText
void drawText(const void* text, size_t byteLength, SkScalar x, SkScalar y, const SkPaint& paint)
Draw text, with origin at (x, y), using Clip, Matrix, and Paint paint.
text meaning depends on Paint Text Encoding; by default, text is encoded as
UTF-8.
x and y meaning depends on Paint Text Align and Paint Vertical Text; by default
text draws left to right, positioning the first glyph left side bearing at x
and its baseline at y. Text size is affected by Matrix and Paint Text Size.
All elements of paint: Path Effect, Mask Filter, Shader,
Color Filter, Image Filter, and Draw Looper; apply to text. By default, draws
filled 12 point black Glyphs.
### Parameters
### Example
### See Also
drawString[2] drawPosText drawPosTextH drawTextBlob[2] drawTextOnPath drawTextRSXform
---
## drawString
void drawString(const char* string, SkScalar x, SkScalar y, const SkPaint& paint)
Draw null terminated string, with origin at (x, y), using Clip, Matrix, and
Paint paint.
string meaning depends on Paint Text Encoding; by default, strings are encoded
as UTF-8. Other values of Paint Text Encoding are unlikely to produce the desired
results, since zero bytes may be embedded in the string.
x and y meaning depends on Paint Text Align and Paint Vertical Text; by default
string draws left to right, positioning the first glyph left side bearing at x
and its baseline at y. Text size is affected by Matrix and Paint Text Size.
All elements of paint: Path Effect, Mask Filter, Shader,
Color Filter, Image Filter, and Draw Looper; apply to text. By default, draws
filled 12 point black Glyphs.
### Parameters
string |
character code points or Glyphs drawn,
ending with a char value of zero |
x |
start of string on x-axis |
y |
start of string on y-axis |
paint |
text size, blend, color, and so on, used to draw |
### Example
### See Also
drawText drawPosText drawPosTextH drawTextBlob[2] drawTextOnPath drawTextRSXform
---
void drawString(const SkString& string, SkScalar x, SkScalar y, const SkPaint& paint)
Draw null terminated string, with origin at (x, y), using Clip, Matrix, and
Paint paint.
string meaning depends on Paint Text Encoding; by default, strings are encoded
as UTF-8. Other values of Paint Text Encoding are unlikely to produce the desired
results, since zero bytes may be embedded in the string.
x and y meaning depends on Paint Text Align and Paint Vertical Text; by default
string draws left to right, positioning the first glyph left side bearing at x
and its baseline at y. Text size is affected by Matrix and Paint Text Size.
All elements of paint: Path Effect, Mask Filter, Shader,
Color Filter, Image Filter, and Draw Looper; apply to text. By default, draws
filled 12 point black Glyphs.
### Parameters
string |
character code points or Glyphs drawn,
ending with a char value of zero |
x |
start of string on x-axis |
y |
start of string on y-axis |
paint |
text size, blend, color, and so on, used to draw |
### Example
### See Also
drawText drawPosText drawPosTextH drawTextBlob[2] drawTextOnPath drawTextRSXform
---
## drawPosText
void drawPosText(const void* text, size_t byteLength, const SkPoint pos[], const SkPaint& paint)
Draw each glyph in text with the origin in pos array, using Clip, Matrix, and
Paint paint. The number of entries in pos array must match the number of Glyphs
described by byteLength of text.
text meaning depends on Paint Text Encoding; by default, text is encoded as
UTF-8. pos elements' meaning depends on Paint Text Align and Paint Vertical Text;
by default each glyph left side bearing is positioned at x and its
baseline is positioned at y. Text size is affected by Matrix and
Paint Text Size.
All elements of paint: Path Effect, Mask Filter, Shader,
Color Filter, Image Filter, and Draw Looper; apply to text. By default, draws
filled 12 point black Glyphs.
Layout engines such as Harfbuzz typically position each glyph
rather than using the font advance widths.
### Parameters
### Example
### See Also
drawText drawPosTextH drawTextBlob[2] drawTextOnPath drawTextRSXform
---
## drawPosTextH
void drawPosTextH(const void* text, size_t byteLength, const SkScalar xpos[], SkScalar constY,
const SkPaint& paint)
Draw each glyph in text with its (x, y) origin composed from xpos array and
constY, using Clip, Matrix, and Paint paint. The number of entries in xpos array
must match the number of Glyphs described by byteLength of text.
text meaning depends on Paint Text Encoding; by default, text is encoded as
UTF-8. xpos elements' meaning depends on Paint Text Align and Paint Vertical Text;
by default each glyph left side bearing is positioned at an xpos element and
its baseline is positioned at constY. Text size is affected by Matrix and
Paint Text Size.
All elements of paint: Path Effect, Mask Filter, Shader,
Color Filter, Image Filter, and Draw Looper; apply to text. By default, draws
filled 12 point black Glyphs.
Layout engines such as Harfbuzz typically position each glyph
rather than using the font advance widths if all Glyphs share the same
baseline.
### Parameters
text |
character code points or Glyphs drawn |
byteLength |
byte length of text array |
xpos |
array of x positions, used to position each glyph |
constY |
shared y coordinate for all of x positions |
paint |
text size, blend, color, and so on, used to draw |
### Example
### See Also
drawText drawPosText drawTextBlob[2] drawTextOnPath drawTextRSXform
---
## drawTextOnPathHV
void drawTextOnPathHV(const void* text, size_t byteLength, const SkPath& path, SkScalar hOffset,
SkScalar vOffset, const SkPaint& paint)
Draw text on Path path, using Clip, Matrix, and Paint paint.
Origin of text is at distance hOffset along the path, offset by a perpendicular
vector of length vOffset. If the path section corresponding the glyph advance is
curved, the glyph is drawn curved to match; control points in the glyph are
mapped to projected points parallel to the path. If the text advance is larger
than the path length, the excess text is clipped.
text meaning depends on Paint Text Encoding; by default, text is encoded as
UTF-8. Origin meaning depends on Paint Text Align and Paint Vertical Text; by
default text positions the first glyph left side bearing at origin x and its
baseline at origin y. Text size is affected by Matrix and Paint Text Size.
All elements of paint: Path Effect, Mask Filter, Shader,
Color Filter, Image Filter, and Draw Looper; apply to text. By default, draws
filled 12 point black Glyphs.
### Parameters
### Example
### See Also
drawTextOnPath drawText drawPosTextH drawTextBlob[2] drawTextRSXform
---
## drawTextOnPath
void drawTextOnPath(const void* text, size_t byteLength, const SkPath& path, const SkMatrix* matrix,
const SkPaint& paint)
Draw text on Path path, using Clip, Matrix, and Paint paint.
Origin of text is at beginning of path offset by matrix, if provided, before it
is mapped to path. If the path section corresponding the glyph advance is
curved, the glyph is drawn curved to match; control points in the glyph are
mapped to projected points parallel to the path. If the text advance is larger
than the path length, the excess text is clipped.
text meaning depends on Paint Text Encoding; by default, text is encoded as
UTF-8. Origin meaning depends on Paint Text Align and Paint Vertical Text; by
default text positions the first glyph left side bearing at origin x and its
baseline at origin y. Text size is affected by Matrix and Paint Text Size.
All elements of paint: Path Effect, Mask Filter, Shader,
Color Filter, Image Filter, and Draw Looper; apply to text. By default, draws
filled 12 point black Glyphs.
### Parameters
### Example
### See Also
drawTextOnPathHV drawText drawPosTextH drawTextBlob[2] drawTextRSXform
---
## drawTextRSXform
void drawTextRSXform(const void* text, size_t byteLength, const SkRSXform xform[],
const SkRect* cullRect, const SkPaint& paint)
Draw text, transforming each glyph by the corresponding SkRSXform,
using Clip, Matrix, and Paint paint.
RSXform array specifies a separate square scale, rotation, and translation for
each glyph.
Optional Rect cullRect is a conservative bounds of text, taking into account
RSXform and paint. If cullRect is outside of Clip, canvas can skip drawing.
All elements of paint: Path Effect, Mask Filter, Shader,
Color Filter, Image Filter, and Draw Looper; apply to text. By default, draws
filled 12 point black Glyphs.
### Parameters
### Example
### See Also
drawTextOnPath drawTextOnPathHV drawText drawPosText drawTextBlob[2]
---
## drawTextBlob
void drawTextBlob(const SkTextBlob* blob, SkScalar x, SkScalar y, const SkPaint& paint)
Draw Text Blob blob at (x, y), using Clip, Matrix, and Paint paint.
blob contains Glyphs, their positions, and paint attributes specific to text:
Typeface, Paint Text Size, Paint Text Scale X, Paint Text Skew X,
Paint Text Align, Paint Hinting, Anti-alias, Paint Fake Bold,
Font Embedded Bitmaps, Full Hinting Spacing, LCD Text, Linear Text,
Subpixel Text, and Paint Vertical Text.
Paint Text Encoding must be set to SkPaint::kGlyphID TextEncoding.
Elements of paint: Path Effect, Mask Filter, Shader, Color Filter,
Image Filter, and Draw Looper; apply to blob.
### Parameters
blob |
Glyphs, positions, and their paints' text size, typeface, and so on |
x |
horizontal offset applied to blob |
y |
vertical offset applied to blob |
paint |
blend, color, stroking, and so on, used to draw |
### Example
### See Also
drawText drawPosText drawPosTextH
---
void drawTextBlob(const sk_sp<SkTextBlob>& blob, SkScalar x, SkScalar y, const SkPaint& paint)
Draw Text Blob blob at (x, y), using Clip, Matrix, and Paint paint.
blob contains Glyphs, their positions, and paint attributes specific to text:
Typeface, Paint Text Size, Paint Text Scale X, Paint Text Skew X,
Paint Text Align, Paint Hinting, Anti-alias, Paint Fake Bold,
Font Embedded Bitmaps, Full Hinting Spacing, LCD Text, Linear Text,
Subpixel Text, and Paint Vertical Text.
Paint Text Encoding must be set to SkPaint::kGlyphID TextEncoding.
Elements of paint: Path Effect, Mask Filter, Shader, Color Filter,
Image Filter, and Draw Looper; apply to blob.
### Parameters
blob |
Glyphs, positions, and their paints' text size, typeface, and so on |
x |
horizontal offset applied to blob |
y |
vertical offset applied to blob |
paint |
blend, color, stroking, and so on, used to draw |
### Example
### See Also
drawText drawPosText drawPosTextH
---
## drawPicture
void drawPicture(const SkPicture* picture)
Draw Picture picture, using Clip and Matrix.
Clip and Matrix are unchanged by picture contents, as if
save was called before and restore was called after drawPicture.
Picture records a series of draw commands for later playback.
### Parameters
picture |
recorded drawing commands to play |
### Example
### See Also
drawDrawable[2] SkPicture SkPicture::playback
---
void drawPicture(const sk_sp<SkPicture>& picture)
Draw Picture picture, using Clip and Matrix.
Clip and Matrix are unchanged by picture contents, as if
save was called before and restore was called after drawPicture.
Picture records a series of draw commands for later playback.
### Parameters
picture |
recorded drawing commands to play |
### Example
### See Also
drawDrawable[2] SkPicture SkPicture::playback
---
void drawPicture(const SkPicture* picture, const SkMatrix* matrix, const SkPaint* paint)
Draw Picture picture, using Clip and Matrix; transforming picture with
Matrix matrix, if provided; and use Paint paint Color Alpha, Color Filter,
Image Filter, and Blend Mode, if provided.
matrix transformation is equivalent to: save, concat, drawPicture, restore.
paint use is equivalent to: saveLayer, drawPicture, restore.
### Parameters
picture |
recorded drawing commands to play |
matrix |
Matrix to rotate, scale, translate, and so on; may be nullptr |
paint |
Paint to apply transparency, filtering, and so on; may be nullptr |
### Example
### See Also
drawDrawable[2] SkPicture SkPicture::playback
---
void drawPicture(const sk_sp<SkPicture>& picture, const SkMatrix* matrix, const SkPaint* paint)
Draw Picture picture, using Clip and Matrix; transforming picture with
Matrix matrix, if provided; and use Paint paint Color Alpha, Color Filter,
Image Filter, and Blend Mode, if provided.
matrix transformation is equivalent to: save, concat, drawPicture, restore.
paint use is equivalent to: saveLayer, drawPicture, restore.
### Parameters
picture |
recorded drawing commands to play |
matrix |
Matrix to rotate, scale, translate, and so on; may be nullptr |
paint |
Paint to apply transparency, filtering, and so on; may be nullptr |
### Example
### See Also
drawDrawable[2] SkPicture SkPicture::playback
---
## drawVertices
void drawVertices(const SkVertices* vertices, SkBlendMode mode, const SkPaint& paint)
Draw Vertices vertices, a triangle mesh, using Clip and Matrix.
If Vertices Texs and Vertices Colors are defined in vertices, and Paint paint
contains Shader, Blend Mode mode combines Vertices Colors with Shader.
### Parameters
### Example
### See Also
drawPatch[2] drawPicture[2][3][4]
---
void drawVertices(const sk_sp<SkVertices>& vertices, SkBlendMode mode, const SkPaint& paint)
Draw Vertices vertices, a triangle mesh, using Clip and Matrix.
If Vertices Texs and Vertices Colors are defined in vertices, and Paint paint
contains Shader, Blend Mode mode combines Vertices Colors with Shader.
### Parameters
### Example
### See Also
drawPatch[2] drawPicture[2][3][4]
---
## drawPatch
void drawPatch(const SkPoint cubics[12], const SkColor colors[4], const SkPoint texCoords[4],
SkBlendMode mode, const SkPaint& paint)
Draws a Coons_Patch: the interpolation of four cubics with shared corners,
associating a color, and optionally a texture coordinate, with each corner.
Coons_Patch uses Clip and Matrix, paint Shader, Color Filter,
Color Alpha, Image Filter, and Blend Mode. If Shader is provided it is treated
as Coons_Patch texture; Blend Mode mode combines Color colors and Shader if
both are provided.
Point array cubics specifies four Cubics starting at the top-left corner,
in clockwise order, sharing every fourth point. The last Cubic ends at the
first point.
Color array color associates colors with corners in top-left, top-right,
bottom-right, bottom-left order.
If paint contains Shader, Point array texCoords maps Shader as texture to
corners in top-left, top-right, bottom-right, bottom-left order.
### Parameters
### Example
### See Also
SeeAlso drawVertices[2] drawPicture[2][3][4]
---
void drawPatch(const SkPoint cubics[12], const SkColor colors[4], const SkPoint texCoords[4],
const SkPaint& paint)
Draws Cubic Coons_Patch: the interpolation of four cubics with shared corners,
associating a color, and optionally a texture coordinate, with each corner.
Coons_Patch uses Clip and Matrix, paint Shader, Color Filter,
Color Alpha, Image Filter, and Blend Mode. If Shader is provided it is treated
as Coons_Patch texture; Blend Mode mode combines Color colors and Shader if
both are provided.
Point array cubics specifies four Cubics starting at the top-left corner,
in clockwise order, sharing every fourth point. The last Cubic ends at the
first point.
Color array color associates colors with corners in top-left, top-right,
bottom-right, bottom-left order.
If paint contains Shader, Point array texCoords maps Shader as texture to
corners in top-left, top-right, bottom-right, bottom-left order.
### Parameters
### Example
### Example
### See Also
SeeAlso drawVertices[2] drawPicture[2][3][4]
---
## drawAtlas
void drawAtlas(const SkImage* atlas, const SkRSXform xform[], const SkRect tex[],
const SkColor colors[], int count, SkBlendMode mode, const SkRect* cullRect,
const SkPaint* paint)
Draw a set of sprites from atlas, using Clip, Matrix, and optional Paint paint.
paint uses Anti-alias, Color Alpha, Color Filter, Image Filter, and Blend Mode
to draw, if present. For each entry in the array, Rect tex locates sprite in
atlas, and RSXform xform transforms it into destination space.
xform, text, and colors if present, must contain count entries.
Optional colors are applied for each sprite using Blend Mode.
Optional cullRect is a conservative bounds of all transformed sprites.
If cullRect is outside of Clip, canvas can skip drawing.
### Parameters
### Example
### See Also
drawBitmap drawImage[2]
---
void drawAtlas(const sk_sp<SkImage>& atlas, const SkRSXform xform[], const SkRect tex[],
const SkColor colors[], int count, SkBlendMode mode, const SkRect* cullRect,
const SkPaint* paint)
Draw a set of sprites from atlas, using Clip, Matrix, and optional Paint paint.
paint uses Anti-alias, Color Alpha, Color Filter, Image Filter, and Blend Mode
to draw, if present. For each entry in the array, Rect tex locates sprite in
atlas, and RSXform xform transforms it into destination space.
xform, text, and colors if present, must contain count entries.
Optional colors is applied for each sprite using Blend Mode.
Optional cullRect is a conservative bounds of all transformed sprites.
If cullRect is outside of Clip, canvas can skip drawing.
### Parameters
### Example
### See Also
drawBitmap drawImage[2]
---
void drawAtlas(const SkImage* atlas, const SkRSXform xform[], const SkRect tex[], int count,
const SkRect* cullRect, const SkPaint* paint)
Draw a set of sprites from atlas, using Clip, Matrix, and optional Paint paint.
paint uses Anti-alias, Color Alpha, Color Filter, Image Filter, and Blend Mode
to draw, if present. For each entry in the array, Rect tex locates sprite in
atlas, and RSXform xform transforms it into destination space.
xform and text must contain count entries.
Optional cullRect is a conservative bounds of all transformed sprites.
If cullRect is outside of Clip, canvas can skip drawing.
### Parameters
### Example
### See Also
drawBitmap drawImage[2]
---
void drawAtlas(const sk_sp<SkImage>& atlas, const SkRSXform xform[], const SkRect tex[], int count,
const SkRect* cullRect, const SkPaint* paint)
Draw a set of sprites from atlas, using Clip, Matrix, and optional Paint paint.
paint uses Anti-alias, Color Alpha, Color Filter, Image Filter, and Blend Mode
to draw, if present. For each entry in the array, Rect tex locates sprite in
atlas, and RSXform xform transforms it into destination space.
xform and text must contain count entries.
Optional cullRect is a conservative bounds of all transformed sprites.
If cullRect is outside of Clip, canvas can skip drawing.
### Parameters
### Example
### See Also
drawBitmap drawImage[2]
---
## drawDrawable
void drawDrawable(SkDrawable* drawable, const SkMatrix* matrix = nullptr)
Draw Drawable drawable using Clip and Matrix, concatenated with
optional matrix.
If Canvas has an asynchronous implementation, as is the case
when it is recording into Picture, then drawable will be referenced,
so that SkDrawable::draw() can be called when the operation is finalized. To force
immediate drawing, call SkDrawable::draw() instead.
### Parameters
drawable |
custom struct encapsulating drawing commands |
matrix |
transformation applied to drawing; may be nullptr |
### Example
### See Also
SkDrawable drawPicture[2][3][4]
---
void drawDrawable(SkDrawable* drawable, SkScalar x, SkScalar y)
Draw Drawable drawable using Clip and Matrix, offset by (x, y).
If Canvas has an asynchronous implementation, as is the case
when it is recording into Picture, then drawable will be referenced,
so that SkDrawable::draw() can be called when the operation is finalized. To force
immediate drawing, call SkDrawable::draw() instead.
### Parameters
drawable |
custom struct encapsulating drawing commands |
x |
offset into Canvas writable pixels in x |
y |
offset into Canvas writable pixels in y |
### Example
### See Also
SkDrawable drawPicture[2][3][4]
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## drawAnnotation
void drawAnnotation(const SkRect& rect, const char key[], SkData* value)
Associate Rect on Canvas with an annotation; a key-value pair, where the key is
a null-terminated utf8 string, and optional value is stored as Data.
Only some canvas implementations, such as recording to Picture, or drawing to
Document PDF, use annotations.
### Parameters
rect |
Rect extent of canvas to annotate |
key |
string used for lookup |
value |
data holding value stored in annotation |
### Example
### See Also
SkPicture SkDocument
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void drawAnnotation(const SkRect& rect, const char key[], const sk_sp<SkData>& value)
Associate Rect on Canvas when an annotation; a key-value pair, where the key is
a null-terminated utf8 string, and optional value is stored as Data.
Only some canvas implementations, such as recording to Picture, or drawing to
Document PDF, use annotations.
### Parameters
rect |
Rect extent of canvas to annotate |
key |
string used for lookup |
value |
data holding value stored in annotation |
### Example
### See Also
SkPicture SkDocument
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## getDrawFilter
SkDrawFilter* getDrawFilter() const
soon
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## setDrawFilter
virtual SkDrawFilter* setDrawFilter(SkDrawFilter* filter)
soon
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## isClipEmpty
virtual bool isClipEmpty() const
Returns true if Clip is empty; that is, nothing will draw.
May do work when called; it should not be called
more often than needed. However, once called, subsequent calls perform no
work until Clip changes.
### Return Value
true if Clip is empty
### Example
#### Example Output
~~~~
clip is not empty
clip is empty
~~~~
### See Also
isClipRect getLocalClipBounds[2] getDeviceClipBounds[2]
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## isClipRect
virtual bool isClipRect() const
Returns true if Clip is Rect and not empty.
Returns false if the clip is empty, or if it is not Rect.
### Return Value
true if Clip is Rect and not empty
### Example
#### Example Output
~~~~
clip is rect
clip is not rect
~~~~
### See Also
isClipEmpty getLocalClipBounds[2] getDeviceClipBounds[2]
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