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skia2/docs/SkPaint_Reference.bmh
Cary Clark 7e69c8f348 fix paint docs 
quick and dirty edit to get the bots green.
Larger edit is in the works to bring docs
related to these changes up to date.

TBR=reed@google.com

Docs-Preview: https://skia.org/?cl=168923
Bug: skia:
Change-Id: I38af409e75e46439288e94de2758b34094d0e08f
Reviewed-on: https://skia-review.googlesource.com/c/168923
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
2018-11-07 02:10:01 +00:00

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#Topic Paint
#Alias Paint_Reference ##
#PhraseDef paint_font_metrics
Typeface, Paint_Text_Size, Paint_Text_Scale_X,
Paint_Text_Skew_X, Paint_Hinting, Anti_Alias, Paint_Fake_Bold,
Font_Embedded_Bitmaps, Full_Hinting_Spacing, LCD_Text, Linear_Text,
and Subpixel_Text
##
#Class SkPaint
#Code
#Populate
##
Paint controls options applied when drawing and measuring. Paint collects all
options outside of the Canvas_Clip and Canvas_Matrix.
Various options apply to text, strokes and fills, and images.
Some options may not be implemented on all platforms; in these cases, setting
the option has no effect. Some options are conveniences that duplicate Canvas
functionality; for instance, text size is identical to matrix scale.
Paint options are rarely exclusive; each option modifies a stage of the drawing
pipeline and multiple pipeline stages may be affected by a single Paint.
Paint collects effects and filters that describe single-pass and multiple-pass
algorithms that alter the drawing geometry, color, and transparency. For instance,
Paint does not directly implement dashing or blur, but contains the objects that do so.
The objects contained by Paint are opaque, and cannot be edited outside of the Paint
to affect it. The implementation is free to defer computations associated with the
Paint, or ignore them altogether. For instance, some GPU implementations draw all
Path geometries with Anti_Aliasing, regardless of how SkPaint::kAntiAlias_Flag
is set in Paint.
Paint describes a single color, a single font, a single image quality, and so on.
Multiple colors are drawn either by using multiple paints or with objects like
Shader attached to Paint.
#Method SkPaint()
#Line # constructs with default values ##
Constructs Paint with default values.
#Table
#Legend
# attribute # default value ##
#Legend ##
# Anti_Alias # false ##
# Blend_Mode # SkBlendMode::kSrcOver ##
# Color # SK_ColorBLACK ##
# Color_Alpha # 255 ##
# Color_Filter # nullptr ##
# Dither # false ##
# Draw_Looper # nullptr ##
# Fake_Bold # false ##
# Filter_Quality # kNone_SkFilterQuality ##
# Font_Embedded_Bitmaps # false ##
# Automatic_Hinting # false ##
# Full_Hinting_Spacing # false ##
# Hinting # kNormal_Hinting ##
# Image_Filter # nullptr ##
# LCD_Text # false ##
# Linear_Text # false ##
# Miter_Limit # 4 ##
# Mask_Filter # nullptr ##
# Path_Effect # nullptr ##
# Shader # nullptr ##
# Style # kFill_Style ##
# Text_Encoding # kUTF8_TextEncoding ##
# Text_Scale_X # 1 ##
# Text_Size # 12 ##
# Text_Skew_X # 0 ##
# Typeface # nullptr ##
# Stroke_Cap # kButt_Cap ##
# Stroke_Join # kMiter_Join ##
# Stroke_Width # 0 ##
# Subpixel_Text # false ##
#Table ##
The flags, text size, hinting, and miter limit may be overridden at compile time by defining
paint default values. The overrides may be included in "SkUserConfig.h" or predefined by the
build system.
#Return default initialized Paint ##
#Example
#ToDo mark this as no output ##
#Height 1
###$ $ redefine markup character so preprocessor commands appear normally
#ifndef SkUserConfig_DEFINED
#define SkUserConfig_DEFINED
#define SkPaintDefaults_Flags 0x01 // always enable antialiasing
#define SkPaintDefaults_TextSize 24.f // double default font size
#define SkPaintDefaults_Hinting 3 // use full hinting
#define SkPaintDefaults_MiterLimit 10.f // use HTML Canvas miter limit setting
#endif
$$$# # restore original markup character
##
##
#Method SkPaint(const SkPaint& paint)
#Line # makes a shallow copy ##
#Populate
#Example
#ToDo why is this double-spaced on Fiddle? ##
SkPaint paint1;
paint1.setColor(SK_ColorRED);
SkPaint paint2(paint1);
paint2.setColor(SK_ColorBLUE);
SkDebugf("SK_ColorRED %c= paint1.getColor()\n", SK_ColorRED == paint1.getColor() ? '=' : '!');
SkDebugf("SK_ColorBLUE %c= paint2.getColor()\n", SK_ColorBLUE == paint2.getColor() ? '=' : '!');
#StdOut
SK_ColorRED == paint1.getColor()
SK_ColorBLUE == paint2.getColor()
##
##
##
#Method SkPaint(SkPaint&& paint)
#Line # moves paint without copying it ##
#Populate
#Example
SkPaint paint;
float intervals[] = { 5, 5 };
paint.setPathEffect(SkDashPathEffect::Make(intervals, SK_ARRAY_COUNT(intervals), 2.5f));
SkPaint dashed(std::move(paint));
SkDebugf("path effect unique: %s\n", dashed.getPathEffect()->unique() ? "true" : "false");
#StdOut
path effect unique: true
##
##
##
# ------------------------------------------------------------------------------
#Method void reset()
#In Constructors
#Line # sets to default values ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setColor(SK_ColorRED);
paint1.reset();
SkDebugf("paint1 %c= paint2", paint1 == paint2 ? '=' : '!');
#StdOut
paint1 == paint2
##
##
##
# ------------------------------------------------------------------------------
#Method ~SkPaint()
#Line # decreases Reference_Count of owned objects ##
#Populate
#NoExample
##
##
# ------------------------------------------------------------------------------
#Subtopic Management
#Line # paint copying, moving, comparing ##
##
#Method SkPaint& operator=(const SkPaint& paint)
#In Management
#Line # makes a shallow copy ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setColor(SK_ColorRED);
paint2 = paint1;
SkDebugf("SK_ColorRED %c= paint1.getColor()\n", SK_ColorRED == paint1.getColor() ? '=' : '!');
SkDebugf("SK_ColorRED %c= paint2.getColor()\n", SK_ColorRED == paint2.getColor() ? '=' : '!');
#StdOut
SK_ColorRED == paint1.getColor()
SK_ColorRED == paint2.getColor()
##
##
##
# ------------------------------------------------------------------------------
#Method SkPaint& operator=(SkPaint&& paint)
#In Management
#Line # moves paint without copying it ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setColor(SK_ColorRED);
paint2 = std::move(paint1);
SkDebugf("SK_ColorRED == paint2.getColor()\n", SK_ColorRED == paint2.getColor() ? '=' : '!');
#StdOut
SK_ColorRED == paint2.getColor()
##
##
##
# ------------------------------------------------------------------------------
#Method bool operator==(const SkPaint& a, const SkPaint& b)
#Line # compares paints for equality ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setColor(SK_ColorRED);
paint2.setColor(0xFFFF0000);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
float intervals[] = { 5, 5 };
paint1.setPathEffect(SkDashPathEffect::Make(intervals, 2, 2.5f));
paint2.setPathEffect(SkDashPathEffect::Make(intervals, 2, 2.5f));
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
#StdOut
paint1 == paint2
paint1 != paint2
##
##
#SeeAlso operator!=(const SkPaint& a, const SkPaint& b)
##
# ------------------------------------------------------------------------------
#Method bool operator!=(const SkPaint& a, const SkPaint& b)
#Line # compares paints for inequality ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setColor(SK_ColorRED);
paint2.setColor(0xFFFF0000);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
SkDebugf("paint1 %c= paint2\n", paint1 != paint2 ? '!' : '=');
#StdOut
paint1 == paint2
paint1 == paint2
##
##
#SeeAlso operator==(const SkPaint& a, const SkPaint& b)
##
# ------------------------------------------------------------------------------
#Method uint32_t getHash() const
#In Management
#Line # returns a shallow hash for equality checks ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setColor(SK_ColorRED);
paint2.setColor(0xFFFF0000);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
SkDebugf("paint1.getHash() %c= paint2.getHash()\n",
paint1.getHash() == paint2.getHash() ? '=' : '!');
#StdOut
paint1 == paint2
paint1.getHash() == paint2.getHash()
##
##
##
# ------------------------------------------------------------------------------
#Subtopic Hinting
#Line # glyph outline adjustment ##
##
#Enum Hinting
#Line # level of glyph outline adjustment ##
#Code
#Populate
##
Hinting adjusts the glyph outlines so that the shape provides a uniform
look at a given point size on font engines that support it. Hinting may have a
muted effect or no effect at all depending on the platform.
The four levels roughly control corresponding features on platforms that use FreeType
as the Font_Engine.
#Const kNo_Hinting 0
#Line # glyph outlines unchanged ##
Leaves glyph outlines unchanged from their native representation.
With FreeType, this is equivalent to the FT_LOAD_NO_HINTING
bit-field constant supplied to FT_Load_Glyph, which indicates that the vector
outline being loaded should not be fitted to the pixel grid but simply scaled
to 26.6 fractional pixels.
##
#Const kSlight_Hinting 1
#Line # minimal modification to improve constrast ##
Modifies glyph outlines minimally to improve constrast.
With FreeType, this is equivalent in spirit to the
FT_LOAD_TARGET_LIGHT value supplied to FT_Load_Glyph. It chooses a
lighter hinting algorithm for non-monochrome modes.
Generated Glyphs may be fuzzy but better resemble their original shape.
##
#Const kNormal_Hinting 2
#Line # glyph outlines modified to improve constrast ##
Modifies glyph outlines to improve constrast. This is the default.
With FreeType, this supplies FT_LOAD_TARGET_NORMAL to FT_Load_Glyph,
choosing the default hinting algorithm, which is optimized for standard
gray-level rendering.
##
#Const kFull_Hinting 3
#Line # modifies glyph outlines for maximum constrast ##
Modifies glyph outlines for maximum constrast. With FreeType, this selects
FT_LOAD_TARGET_LCD or FT_LOAD_TARGET_LCD_V if kLCDRenderText_Flag is set.
FT_LOAD_TARGET_LCD is a variant of FT_LOAD_TARGET_NORMAL optimized for
horizontally decimated LCD displays; FT_LOAD_TARGET_LCD_V is a
variant of FT_LOAD_TARGET_NORMAL optimized for vertically decimated LCD displays.
##
#Bug 915
On OS_X and iOS, hinting controls whether Core_Graphics dilates the font outlines
to account for LCD text. No hinting uses Core_Text grayscale output.
Normal hinting uses Core_Text LCD output. If kLCDRenderText_Flag is clear,
the LCD output is reduced to a single grayscale channel.
On Windows with DirectWrite, Hinting has no effect.
Hinting defaults to kNormal_Hinting.
Set SkPaintDefaults_Hinting at compile time to change the default setting.
#ToDo add an illustration? linux running GM:typefacerendering is best for this
the hinting variations are every other character horizontally
#ToDo ##
#Enum ##
#Method Hinting getHinting() const
#In Hinting
#Line # returns Hinting, glyph outline adjustment level ##
#Populate
#Example
SkPaint paint;
SkDebugf("SkPaint::kNormal_Hinting %c= paint.getHinting()\n",
SkPaint::kNormal_Hinting == paint.getHinting() ? '=' : ':');
#StdOut
SkPaint::kNormal_Hinting == paint.getHinting()
##
##
##
#Method void setHinting(SkFontHinting hintingLevel)
#In Hinting
#Line # sets Hinting, glyph outline adjustment level ##
#Populate
#Example
SkPaint paint1, paint2;
paint2.setHinting(kNormal_SkFontHinting);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : ':');
#StdOut
paint1 == paint2
##
##
##
#Method void setHinting(Hinting hintingLevel)
#In Hinting
#Populate
#Example
SkPaint paint1, paint2;
paint2.setHinting(SkPaint::kNormal_Hinting);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : ':');
#StdOut
paint1 == paint2
##
##
##
# ------------------------------------------------------------------------------
#Subtopic Flags
#Line # attributes represented by single bits ##
##
#Enum Flags
#Line # values described by bits and masks ##
#Code
#Populate
##
The bit values stored in Flags.
The default value for Flags, normally zero, can be changed at compile time
with a custom definition of SkPaintDefaults_Flags.
All flags can be read and written explicitly; Flags allows manipulating
multiple settings at once.
#Const kAntiAlias_Flag 0x0001
#Line # mask for setting Anti_Alias ##
##
#Const kDither_Flag 0x0004
#Line # mask for setting Dither ##
##
#Const kFakeBoldText_Flag 0x0020
#Line # mask for setting Fake_Bold ##
##
#Const kLinearText_Flag 0x0040
#Line # mask for setting Linear_Text ##
##
#Const kSubpixelText_Flag 0x0080
#Line # mask for setting Subpixel_Text ##
##
#Const kLCDRenderText_Flag 0x0200
#Line # mask for setting LCD_Text ##
##
#Const kEmbeddedBitmapText_Flag 0x0400
#Line # mask for setting Font_Embedded_Bitmaps ##
##
#Const kAutoHinting_Flag 0x0800
#Line # mask for setting Automatic_Hinting ##
##
#Const kAllFlags 0xFFFF
#Line # mask of all Flags ##
mask of all Flags, including private flags and flags reserved for future use
##
Flags default to all flags clear, disabling the associated feature.
#Enum ##
#Enum ReserveFlags
#Deprecated soon
Only valid for Android framework.
#Code
#Populate
##
#Const kUnderlineText_ReserveFlag 0x0008
#Deprecated soon
##
#Const kStrikeThruText_ReserveFlag 0x0010
#Deprecated soon
##
##
#Method uint32_t getFlags() const
#In Flags
#Line # returns Flags stored in a bit field ##
#Populate
#Example
SkPaint paint;
paint.setAntiAlias(true);
SkDebugf("(SkPaint::kAntiAlias_Flag & paint.getFlags()) %c= 0\n",
SkPaint::kAntiAlias_Flag & paint.getFlags() ? '!' : '=');
#StdOut
(SkPaint::kAntiAlias_Flag & paint.getFlags()) != 0
##
##
##
#Method void setFlags(uint32_t flags)
#In Flags
#Line # sets multiple Flags in a bit field ##
#Populate
#Example
SkPaint paint;
paint.setFlags((uint32_t) (SkPaint::kAntiAlias_Flag | SkPaint::kDither_Flag));
SkDebugf("paint.isAntiAlias()\n", paint.isAntiAlias() ? '!' : '=');
SkDebugf("paint.isDither()\n", paint.isDither() ? '!' : '=');
#StdOut
paint.isAntiAlias()
paint.isDither()
##
##
##
# ------------------------------------------------------------------------------
#Subtopic Anti_Alias
#Alias Anti_Alias
#Substitute anti-alias
##
#Alias Anti_Aliased
#Substitute anti-aliased
##
#Alias Anti_Aliasing
#Substitute anti-aliasing
##
#In Related_Function
#Line # approximating coverage with transparency ##
Anti_Alias drawing approximates partial pixel coverage with transparency.
If kAntiAlias_Flag is clear, pixel centers contained by the shape edge are drawn opaque.
If kAntiAlias_Flag is set, pixels are drawn with Color_Alpha equal to their coverage.
The rule for Aliased pixels is inconsistent across platforms. A shape edge
passing through the pixel center may, but is not required to, draw the pixel.
Raster_Engine draws Aliased pixels whose centers are on or to the right of the start of an
active Path edge, and whose center is to the left of the end of the active Path edge.
#ToDo add illustration of raster pixels ##
A platform may only support Anti_Aliased drawing. Some GPU-backed platforms use
Supersampling to Anti_Alias all drawing, and have no mechanism to selectively
Alias.
The amount of coverage computed for Anti_Aliased pixels also varies across platforms.
Anti_Alias is disabled by default.
Anti_Alias can be enabled by default by setting SkPaintDefaults_Flags to kAntiAlias_Flag
at compile time.
#Example
#Width 512
#Description
A red line is drawn with transparency on the edges to make it look smoother.
A blue line draws only where the pixel centers are contained.
The lines are drawn into Bitmap, then drawn magnified to make the
Aliasing easier to see.
##
void draw(SkCanvas* canvas) {
SkBitmap bitmap;
bitmap.allocN32Pixels(50, 50);
SkCanvas offscreen(bitmap);
SkPaint paint;
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(10);
for (bool antialias : { false, true }) {
paint.setColor(antialias ? SK_ColorRED : SK_ColorBLUE);
paint.setAntiAlias(antialias);
bitmap.eraseColor(0);
offscreen.drawLine(5, 5, 15, 30, paint);
canvas->drawLine(5, 5, 15, 30, paint);
canvas->save();
canvas->scale(10, 10);
canvas->drawBitmap(bitmap, antialias ? 12 : 0, 0);
canvas->restore();
canvas->translate(15, 0);
}
}
##
#Subtopic Anti_Alias ##
#Method bool isAntiAlias() const
#In Anti_alias
#Line # returns true if Anti_Alias is set ##
#Populate
#Example
SkPaint paint;
SkDebugf("paint.isAntiAlias() %c= !!(paint.getFlags() & SkPaint::kAntiAlias_Flag)\n",
paint.isAntiAlias() == !!(paint.getFlags() & SkPaint::kAntiAlias_Flag) ? '=' : '!');
paint.setAntiAlias(true);
SkDebugf("paint.isAntiAlias() %c= !!(paint.getFlags() & SkPaint::kAntiAlias_Flag)\n",
paint.isAntiAlias() == !!(paint.getFlags() & SkPaint::kAntiAlias_Flag) ? '=' : '!');
#StdOut
paint.isAntiAlias() == !!(paint.getFlags() & SkPaint::kAntiAlias_Flag)
paint.isAntiAlias() == !!(paint.getFlags() & SkPaint::kAntiAlias_Flag)
##
##
##
#Method void setAntiAlias(bool aa)
#In Anti_alias
#Line # sets or clears Anti_Alias ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setAntiAlias(true);
paint2.setFlags(paint2.getFlags() | SkPaint::kAntiAlias_Flag);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
#StdOut
paint1 == paint2
##
##
##
# ------------------------------------------------------------------------------
#Subtopic Dither
#Line # distributing color error ##
Dither increases fidelity by adjusting the color of adjacent pixels.
This can help to smooth color transitions and reducing banding in gradients.
Dithering lessens visible banding from kRGB_565_SkColorType
and kRGBA_8888_SkColorType gradients,
and improves rendering into a kRGB_565_SkColorType Surface.
Dithering is always enabled for linear gradients drawing into
kRGB_565_SkColorType Surface and kRGBA_8888_SkColorType Surface.
Dither cannot be enabled for kAlpha_8_SkColorType Surface and
kRGBA_F16_SkColorType Surface.
Dither is disabled by default.
Dither can be enabled by default by setting SkPaintDefaults_Flags to kDither_Flag
at compile time.
Some platform implementations may ignore dithering. Set #Formula # SK_IGNORE_GPU_DITHER ##
to ignore Dither on GPU_Surface.
#Example
#Description
Dithering in the bottom half more closely approximates the requested color by
alternating nearby colors from pixel to pixel.
##
void draw(SkCanvas* canvas) {
SkBitmap bm16;
bm16.allocPixels(SkImageInfo::Make(32, 32, kRGB_565_SkColorType, kOpaque_SkAlphaType));
SkCanvas c16(bm16);
SkPaint colorPaint;
for (auto dither : { false, true } ) {
colorPaint.setDither(dither);
for (auto colors : { 0xFF333333, 0xFF666666, 0xFF999999, 0xFFCCCCCC } ) {
for (auto mask : { 0xFFFF0000, 0xFF00FF00, 0xFF0000FF, 0xFFFFFFFF } ) {
colorPaint.setColor(colors & mask);
c16.drawRect({0, 0, 8, 4}, colorPaint);
c16.translate(8, 0);
}
c16.translate(-32, 4);
}
}
canvas->scale(8, 8);
canvas->drawBitmap(bm16, 0, 0);
}
##
#Example
#Description
Dithering introduces subtle adjustments to color to smooth gradients.
Drawing the gradient repeatedly with SkBlendMode::kPlus exaggerates the
dither, making it easier to see.
##
void draw(SkCanvas* canvas) {
canvas->clear(0);
SkBitmap bm32;
bm32.allocPixels(SkImageInfo::Make(20, 10, kN32_SkColorType, kPremul_SkAlphaType));
SkCanvas c32(bm32);
SkPoint points[] = {{0, 0}, {20, 0}};
SkColor colors[] = {0xFF334455, 0xFF662211 };
SkPaint paint;
paint.setShader(SkGradientShader::MakeLinear(
points, colors, nullptr, SK_ARRAY_COUNT(colors),
SkShader::kClamp_TileMode, 0, nullptr));
paint.setDither(true);
c32.drawPaint(paint);
canvas->scale(12, 12);
canvas->drawBitmap(bm32, 0, 0);
paint.setBlendMode(SkBlendMode::kPlus);
canvas->drawBitmap(bm32, 0, 11, &paint);
canvas->drawBitmap(bm32, 0, 11, &paint);
canvas->drawBitmap(bm32, 0, 11, &paint);
}
##
#SeeAlso Gradient kRGB_565_SkColorType
#Subtopic Dither ##
#Method bool isDither() const
#In Dither
#Line # returns true if Dither is set ##
#Populate
#Example
SkPaint paint;
SkDebugf("paint.isDither() %c= !!(paint.getFlags() & SkPaint::kDither_Flag)\n",
paint.isDither() == !!(paint.getFlags() & SkPaint::kDither_Flag) ? '=' : '!');
paint.setDither(true);
SkDebugf("paint.isDither() %c= !!(paint.getFlags() & SkPaint::kDither_Flag)\n",
paint.isDither() == !!(paint.getFlags() & SkPaint::kDither_Flag) ? '=' : '!');
#StdOut
paint.isDither() == !!(paint.getFlags() & SkPaint::kDither_Flag)
paint.isDither() == !!(paint.getFlags() & SkPaint::kDither_Flag)
##
##
##
#Method void setDither(bool dither)
#In Dither
#Line # sets or clears Dither ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setDither(true);
paint2.setFlags(paint2.getFlags() | SkPaint::kDither_Flag);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
#StdOut
paint1 == paint2
##
##
#SeeAlso kRGB_565_SkColorType
##
# ------------------------------------------------------------------------------
#Subtopic Device_Text
#Line # increase precision of glyph position ##
LCD_Text and Subpixel_Text increase the precision of glyph position.
When set, Flags kLCDRenderText_Flag takes advantage of the organization of RGB stripes that
create a color, and relies
on the small size of the stripe and visual perception to make the color fringing imperceptible.
LCD_Text can be enabled on devices that orient stripes horizontally or vertically, and that order
the color components as RGB or BGR.
Flags kSubpixelText_Flag uses the pixel transparency to represent a fractional offset.
As the opaqueness
of the color increases, the edge of the glyph appears to move towards the outside of the pixel.
Either or both techniques can be enabled.
kLCDRenderText_Flag and kSubpixelText_Flag are clear by default.
LCD_Text or Subpixel_Text can be enabled by default by setting SkPaintDefaults_Flags to
kLCDRenderText_Flag or kSubpixelText_Flag (or both) at compile time.
#Example
#Description
Four commas are drawn normally and with combinations of LCD_Text and Subpixel_Text.
When Subpixel_Text is disabled, the comma Glyphs are identical, but not evenly spaced.
When Subpixel_Text is enabled, the comma Glyphs are unique, but appear evenly spaced.
##
SkBitmap bitmap;
bitmap.allocN32Pixels(24, 33);
SkCanvas offscreen(bitmap);
offscreen.clear(SK_ColorWHITE);
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(20);
for (bool lcd : { false, true }) {
paint.setLCDRenderText(lcd);
for (bool subpixel : { false, true }) {
paint.setSubpixelText(subpixel);
offscreen.drawString(",,,,", 0, 4, paint);
offscreen.translate(0, 7);
}
}
canvas->drawBitmap(bitmap, 4, 12);
canvas->scale(9, 9);
canvas->drawBitmap(bitmap, 4, -1);
##
#Subtopic Device_Text ##
#Subtopic Linear_Text
#Alias Linear_Text ##
#Line # selects text rendering as Glyph or Path ##
Linear_Text selects whether text is rendered as a Glyph or as a Path.
If kLinearText_Flag is set, it has the same effect as setting Hinting to kNormal_Hinting.
If kLinearText_Flag is clear, it is the same as setting Hinting to kNo_Hinting.
#Subtopic Linear_Text ##
#Method bool isLinearText() const
#In Linear_Text
#Line # returns true if text is converted to Path ##
#Populate
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setAntiAlias(true);
const char testStr[] = "xxxx xxxx";
for (auto linearText : { false, true } ) {
paint.setLinearText(linearText);
paint.setTextSize(24);
canvas->drawString(paint.isLinearText() ? "linear" : "hinted", 128, 30, paint);
for (SkScalar textSize = 8; textSize < 30; textSize *= 1.22f) {
paint.setTextSize(textSize);
canvas->translate(0, textSize);
canvas->drawString(testStr, 10, 0, paint);
}
}
}
##
#SeeAlso setLinearText Hinting
##
#Method void setLinearText(bool linearText)
#In Linear_Text
#Line # converts to Path before draw or measure ##
#Populate
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setAntiAlias(true);
const char testStr[] = "abcd efgh";
for (int textSize : { 12, 24 } ) {
paint.setTextSize(textSize);
for (auto linearText : { false, true } ) {
paint.setLinearText(linearText);
SkString width;
width.appendScalar(paint.measureText(testStr, SK_ARRAY_COUNT(testStr), nullptr));
canvas->translate(0, textSize + 4);
canvas->drawString(testStr, 10, 0, paint);
canvas->drawString(width, 128, 0, paint);
}
}
}
##
#SeeAlso isLinearText Hinting
##
#Subtopic Subpixel_Text
#Alias Subpixel_Text ##
#Line # uses pixel transparency to represent fractional offset ##
Flags kSubpixelText_Flag uses the pixel transparency to represent a fractional offset.
As the opaqueness
of the color increases, the edge of the glyph appears to move towards the outside of the pixel.
#Subtopic Subpixel_Text ##
#Method bool isSubpixelText() const
#In Subpixel_Text
#Line # returns true if Subpixel_Text is set ##
#Populate
#Example
SkPaint paint;
SkDebugf("paint.isSubpixelText() %c= !!(paint.getFlags() & SkPaint::kSubpixelText_Flag)\n",
paint.isSubpixelText() == !!(paint.getFlags() & SkPaint::kSubpixelText_Flag) ? '=' : '!');
paint.setSubpixelText(true);
SkDebugf("paint.isSubpixelText() %c= !!(paint.getFlags() & SkPaint::kSubpixelText_Flag)\n",
paint.isSubpixelText() == !!(paint.getFlags() & SkPaint::kSubpixelText_Flag) ? '=' : '!');
#StdOut
paint.isSubpixelText() == !!(paint.getFlags() & SkPaint::kSubpixelText_Flag)
paint.isSubpixelText() == !!(paint.getFlags() & SkPaint::kSubpixelText_Flag)
##
##
##
#Method void setSubpixelText(bool subpixelText)
#In Subpixel_Text
#Line # sets or clears Subpixel_Text ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setSubpixelText(true);
paint2.setFlags(paint2.getFlags() | SkPaint::kSubpixelText_Flag);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
#StdOut
paint1 == paint2
##
##
##
#Subtopic LCD_Text
#Line # text relying on the order of RGB stripes ##
# make this a top level name, since it is under subtopic Device_Text
#Alias LCD_Text
#Substitute LCD text
##
When set, Flags kLCDRenderText_Flag takes advantage of the organization of RGB stripes that
create a color, and relies
on the small size of the stripe and visual perception to make the color fringing imperceptible.
LCD_Text can be enabled on devices that orient stripes horizontally or vertically, and that order
the color components as RGB or BGR.
#Subtopic LCD_Text ##
#Method bool isLCDRenderText() const
#In LCD_Text
#Line # returns true if LCD_Text is set ##
#Populate
#Example
SkPaint paint;
SkDebugf("paint.isLCDRenderText() %c= !!(paint.getFlags() & SkPaint::kLCDRenderText_Flag)\n",
paint.isLCDRenderText() == !!(paint.getFlags() & SkPaint::kLCDRenderText_Flag) ? '=' : '!');
paint.setLCDRenderText(true);
SkDebugf("paint.isLCDRenderText() %c= !!(paint.getFlags() & SkPaint::kLCDRenderText_Flag)\n",
paint.isLCDRenderText() == !!(paint.getFlags() & SkPaint::kLCDRenderText_Flag) ? '=' : '!');
#StdOut
paint.isLCDRenderText() == !!(paint.getFlags() & SkPaint::kLCDRenderText_Flag)
paint.isLCDRenderText() == !!(paint.getFlags() & SkPaint::kLCDRenderText_Flag)
##
##
##
#Method void setLCDRenderText(bool lcdText)
#In LCD_Text
#Line # sets or clears LCD_Text ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setLCDRenderText(true);
paint2.setFlags(paint2.getFlags() | SkPaint::kLCDRenderText_Flag);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
#StdOut
paint1 == paint2
##
##
##
# ------------------------------------------------------------------------------
#Subtopic Font_Embedded_Bitmaps
#Line # custom sized bitmap Glyphs ##
#Alias Font_Embedded_Bitmaps ## # long-winded enough, alias so I don't type Paint_Font_...
Font_Embedded_Bitmaps allows selecting custom sized bitmap Glyphs.
Flags kEmbeddedBitmapText_Flag when set chooses an embedded bitmap glyph over an outline contained
in a font if the platform supports this option.
FreeType selects the bitmap glyph if available when kEmbeddedBitmapText_Flag is set, and selects
the outline glyph if kEmbeddedBitmapText_Flag is clear.
Windows may select the bitmap glyph but is not required to do so.
OS_X and iOS do not support this option.
Font_Embedded_Bitmaps is disabled by default.
Font_Embedded_Bitmaps can be enabled by default by setting SkPaintDefaults_Flags to
kEmbeddedBitmapText_Flag at compile time.
#Example
#ToDo image will only output on Ubuntu ... how to handle that in fiddle? ##
#Platform !fiddle
#Description
The "hintgasp" TrueType font in the Skia resources/fonts directory
includes an embedded bitmap Glyph at odd font sizes. This example works
on platforms that use FreeType as their Font_Engine.
Windows may, but is not required to, return a bitmap glyph if
kEmbeddedBitmapText_Flag is set.
##
#Image embeddedbitmap.png
SkBitmap bitmap;
bitmap.allocN32Pixels(30, 15);
bitmap.eraseColor(0);
SkCanvas offscreen(bitmap);
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(13);
paint.setTypeface(MakeResourceAsTypeface("fonts/hintgasp.ttf"));
for (bool embedded : { false, true}) {
paint.setEmbeddedBitmapText(embedded);
offscreen.drawString("A", embedded ? 5 : 15, 15, paint);
}
canvas->drawBitmap(bitmap, 0, 0);
canvas->scale(10, 10);
canvas->drawBitmap(bitmap, -2, 1);
##
#Subtopic Font_Embedded_Bitmaps ##
#Method bool isEmbeddedBitmapText() const
#In Font_Embedded_Bitmaps
#Line # returns true if Font_Embedded_Bitmaps is set ##
#Populate
#Example
SkPaint paint;
SkDebugf("paint.isEmbeddedBitmapText() %c="
" !!(paint.getFlags() & SkPaint::kEmbeddedBitmapText_Flag)\n",
paint.isEmbeddedBitmapText() ==
!!(paint.getFlags() & SkPaint::kEmbeddedBitmapText_Flag) ? '=' : '!');
paint.setEmbeddedBitmapText(true);
SkDebugf("paint.isEmbeddedBitmapText() %c="
" !!(paint.getFlags() & SkPaint::kEmbeddedBitmapText_Flag)\n",
paint.isEmbeddedBitmapText() ==
!!(paint.getFlags() & SkPaint::kEmbeddedBitmapText_Flag) ? '=' : '!');
#StdOut
paint.isEmbeddedBitmapText() == !!(paint.getFlags() & SkPaint::kEmbeddedBitmapText_Flag)
paint.isEmbeddedBitmapText() == !!(paint.getFlags() & SkPaint::kEmbeddedBitmapText_Flag)
##
##
##
#Method void setEmbeddedBitmapText(bool useEmbeddedBitmapText)
#In Font_Embedded_Bitmaps
#Line # sets or clears Font_Embedded_Bitmaps ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setEmbeddedBitmapText(true);
paint2.setFlags(paint2.getFlags() | SkPaint::kEmbeddedBitmapText_Flag);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
#StdOut
paint1 == paint2
##
##
##
# ------------------------------------------------------------------------------
#Subtopic Automatic_Hinting
#Line # always adjust glyph paths ##
#Substitute auto-hinting
If Hinting is set to kNormal_Hinting or kFull_Hinting, Automatic_Hinting
instructs the Font_Manager to always hint Glyphs.
Automatic_Hinting has no effect if Hinting is set to kNo_Hinting or
kSlight_Hinting.
Automatic_Hinting only affects platforms that use FreeType as the Font_Manager.
#Subtopic Automatic_Hinting ##
#Method bool isAutohinted() const
#In Automatic_Hinting
#Line # returns true if Glyphs are always hinted ##
#Populate
#Example
SkPaint paint;
for (auto forceAutoHinting : { false, true} ) {
paint.setAutohinted(forceAutoHinting);
SkDebugf("paint.isAutohinted() %c="
" !!(paint.getFlags() & SkPaint::kAutoHinting_Flag)\n",
paint.isAutohinted() ==
!!(paint.getFlags() & SkPaint::kAutoHinting_Flag) ? '=' : '!');
}
#StdOut
paint.isAutohinted() == !!(paint.getFlags() & SkPaint::kAutoHinting_Flag)
paint.isAutohinted() == !!(paint.getFlags() & SkPaint::kAutoHinting_Flag)
##
##
#SeeAlso setAutohinted Hinting
##
#Method void setAutohinted(bool useAutohinter)
#In Automatic_Hinting
#Line # sets Glyphs to always be hinted ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setAntiAlias(true);
const char testStr[] = "xxxx xxxx";
for (auto forceAutoHinting : { false, true} ) {
paint.setAutohinted(forceAutoHinting);
paint.setTextSize(24);
canvas->drawString(paint.isAutohinted() ? "auto-hinted" : "default", 108, 30, paint);
for (SkScalar textSize = 8; textSize < 30; textSize *= 1.22f) {
paint.setTextSize(textSize);
canvas->translate(0, textSize);
canvas->drawString(testStr, 10, 0, paint);
}
}
}
##
#SeeAlso isAutohinted Hinting
##
# ------------------------------------------------------------------------------
#Subtopic Fake_Bold
#Line # approximate font styles ##
Fake_Bold approximates the bold font style accompanying a normal font when a bold font face
is not available. Skia does not provide font substitution; it is up to the client to find the
bold font face using the platform Font_Manager.
Use Text_Skew_X to approximate an italic font style when the italic font face
is not available.
A FreeType based port may define SK_USE_FREETYPE_EMBOLDEN at compile time to direct
the font engine to create the bold Glyphs. Otherwise, the extra bold is computed
by increasing the stroke width and setting the Style to kStrokeAndFill_Style as needed.
Fake_Bold is disabled by default.
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(40);
canvas->drawString("OjYy_-", 10, 35, paint);
paint.setFakeBoldText(true);
canvas->drawString("OjYy_-", 10, 75, paint);
// create a custom fake bold by varying the stroke width
paint.setFakeBoldText(false);
paint.setStyle(SkPaint::kStrokeAndFill_Style);
paint.setStrokeWidth(40.f / 48);
canvas->drawString("OjYy_-", 10, 115, paint);
}
##
#Subtopic Fake_Bold ##
#Method bool isFakeBoldText() const
#In Fake_Bold
#Line # returns true if Fake_Bold is set ##
#Populate
#Example
SkPaint paint;
SkDebugf("paint.isFakeBoldText() %c= !!(paint.getFlags() & SkPaint::kFakeBoldText_Flag)\n",
paint.isFakeBoldText() == !!(paint.getFlags() & SkPaint::kFakeBoldText_Flag) ? '=' : '!');
paint.setFakeBoldText(true);
SkDebugf("paint.isFakeBoldText() %c= !!(paint.getFlags() & SkPaint::kFakeBoldText_Flag)\n",
paint.isFakeBoldText() == !!(paint.getFlags() & SkPaint::kFakeBoldText_Flag) ? '=' : '!');
#StdOut
paint.isFakeBoldText() == !!(paint.getFlags() & SkPaint::kFakeBoldText_Flag)
paint.isFakeBoldText() == !!(paint.getFlags() & SkPaint::kFakeBoldText_Flag)
##
##
##
#Method void setFakeBoldText(bool fakeBoldText)
#In Fake_Bold
#Line # sets or clears Fake_Bold ##
#Populate
#Example
SkPaint paint1, paint2;
paint1.setFakeBoldText(true);
paint2.setFlags(paint2.getFlags() | SkPaint::kFakeBoldText_Flag);
SkDebugf("paint1 %c= paint2\n", paint1 == paint2 ? '=' : '!');
#StdOut
paint1 == paint2
##
##
##
# ------------------------------------------------------------------------------
#Subtopic Full_Hinting_Spacing
#Line # glyph spacing affected by hinting ##
#Alias Full_Hinting_Spacing ## # long winded enough -- maybe things with two underscores auto-aliased?
if Hinting is set to kFull_Hinting, Full_Hinting_Spacing adjusts the character
spacing by the difference of the hinted and unhinted Left_Side_Bearing and
Right_Side_Bearing. Full_Hinting_Spacing only applies to platforms that use
FreeType as their Font_Engine.
Full_Hinting_Spacing is not related to text kerning, where the space between
a specific pair of characters is adjusted using data in the font kerning tables.
#Subtopic Full_Hinting_Spacing ##
# ------------------------------------------------------------------------------
#Subtopic Filter_Quality_Methods
#Line # get and set Filter_Quality ##
Filter_Quality trades speed for image filtering when the image is scaled.
A lower Filter_Quality draws faster, but has less fidelity.
A higher Filter_Quality draws slower, but looks better.
If the image is drawn without scaling, the Filter_Quality choice will not result
in a noticeable difference.
Filter_Quality is used in Paint passed as a parameter to
#List
# SkCanvas::drawBitmap ##
# SkCanvas::drawBitmapRect ##
# SkCanvas::drawImage ##
# SkCanvas::drawImageRect ##
#ToDo probably more... ##
#List ##
and when Paint has a Shader specialization that uses Image or Bitmap.
Filter_Quality is kNone_SkFilterQuality by default.
#Example
#Image 3
void draw(SkCanvas* canvas) {
SkPaint paint;
canvas->scale(.2f, .2f);
for (SkFilterQuality q : { kNone_SkFilterQuality, kLow_SkFilterQuality,
kMedium_SkFilterQuality, kHigh_SkFilterQuality } ) {
paint.setFilterQuality(q);
canvas->drawImage(image.get(), 0, 0, &paint);
canvas->translate(550, 0);
if (kLow_SkFilterQuality == q) canvas->translate(-1100, 550);
}
}
##
#Subtopic Filter_Quality_Methods ##
#Method SkFilterQuality getFilterQuality() const
#In Filter_Quality_Methods
#Line # returns Filter_Quality, image filtering level ##
#Populate
#Example
SkPaint paint;
SkDebugf("kNone_SkFilterQuality %c= paint.getFilterQuality()\n",
kNone_SkFilterQuality == paint.getFilterQuality() ? '=' : '!');
#StdOut
kNone_SkFilterQuality == paint.getFilterQuality()
##
##
##
#Method void setFilterQuality(SkFilterQuality quality)
#In Filter_Quality_Methods
#Line # sets Filter_Quality, the image filtering level ##
#Populate
#Example
SkPaint paint;
paint.setFilterQuality(kHigh_SkFilterQuality);
SkDebugf("kHigh_SkFilterQuality %c= paint.getFilterQuality()\n",
kHigh_SkFilterQuality == paint.getFilterQuality() ? '=' : '!');
#StdOut
kHigh_SkFilterQuality == paint.getFilterQuality()
##
##
#SeeAlso SkFilterQuality Image_Scaling
##
# ------------------------------------------------------------------------------
#Subtopic Color_Methods
#Line # get and set Color ##
#Table
#Legend
# name # description ##
#Legend ##
# getColor # returns Color_Alpha and RGB, one drawing color ##
# setColor # sets Color_Alpha and RGB, one drawing color ##
#Table ##
Color specifies the red, blue, green, and Color_Alpha
values used to draw a filled or stroked shape in a 32-bit value. Each component
occupies 8-bits, ranging from zero: no contribution; to 255: full intensity.
All values in any combination are valid.
Color is not Premultiplied; Color_Alpha sets the transparency independent of
RGB: red, blue, and green.
The bit positions of Color_Alpha and RGB are independent of the bit
positions on the output device, which may have more or fewer bits, and may have
a different arrangement.
#Table
#Legend
# bit positions # Color_Alpha # red # blue # green ##
#Legend ##
# # 31 - 24 # 23 - 16 # 15 - 8 # 7 - 0 ##
#Table ##
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setColor(0x8000FF00); // transparent green
canvas->drawCircle(50, 50, 40, paint);
paint.setARGB(128, 255, 0, 0); // transparent red
canvas->drawCircle(80, 50, 40, paint);
paint.setColor(SK_ColorBLUE);
paint.setAlpha(0x80);
canvas->drawCircle(65, 65, 40, paint);
}
##
#Subtopic Color_Methods ##
#Method SkColor getColor() const
#In Color_Methods
#Line # returns Color_Alpha and RGB, one drawing color ##
#Populate
#Example
SkPaint paint;
paint.setColor(SK_ColorYELLOW);
SkColor y = paint.getColor();
SkDebugf("Yellow is %d%% red, %d%% green, and %d%% blue.\n", (int) (SkColorGetR(y) / 2.55f),
(int) (SkColorGetG(y) / 2.55f), (int) (SkColorGetB(y) / 2.55f));
#StdOut
Yellow is 100% red, 100% green, and 0% blue.
##
##
#SeeAlso getColor4f SkColor
##
#Method SkColor4f getColor4f() const
#In Color_Methods
#Line # returns Color_Alpha and RGB, one drawing color ##
#Populate
#Example
SkPaint paint;
paint.setColor(SK_ColorYELLOW);
SkColor4f y = paint.getColor4f();
SkDebugf("Yellow is %d%% red, %d%% green, and %d%% blue.\n", (int) (y.fR * 100),
(int) (y.fG * 100), (int) (y.fB * 100));
#StdOut
Yellow is 100% red, 100% green, and 0% blue.
##
##
#SeeAlso getColor SkColor
##
#Method void setColor(SkColor color)
#In Color_Methods
#Line # sets Color_Alpha and RGB, one drawing color ##
#Populate
#Example
SkPaint green1, green2;
unsigned a = 255;
unsigned r = 0;
unsigned g = 255;
unsigned b = 0;
green1.setColor((a << 24) + (r << 16) + (g << 8) + (b << 0));
green2.setColor(0xFF00FF00);
SkDebugf("green1 %c= green2\n", green1 == green2 ? '=' : '!');
#StdOut
green1 == green2
##
##
#SeeAlso SkColor setColor4f setARGB SkColorSetARGB
##
#Method void setColor4f(const SkColor4f& color, SkColorSpace* colorSpace)
#In Color_Methods
#Line # sets Color_Alpha and RGB, one drawing color ##
#Populate
#Example
SkPaint green1, green2;
green1.setColor4f({0, 1, 0, 1}, nullptr); // R=0 G=1 B=0 A=1
green2.setColor(0xFF00FF00); // A=255 R=0 G=255 B=0
SkDebugf("green1 %c= green2\n", green1 == green2 ? '=' : '!');
#StdOut
green1 == green2
##
##
#SeeAlso SkColor setColor setARGB SkColorSetARGB
##
#Subtopic Alpha_Methods
#Line # get and set Alpha ##
Color_Alpha sets the transparency independent of RGB: red, blue, and green.
#Subtopic Alpha_Methods ##
#Method uint8_t getAlpha() const
#In Alpha_Methods
#Line # returns Color_Alpha, color opacity ##
#Populate
#Example
SkPaint paint;
SkDebugf("255 %c= paint.getAlpha()\n", 255 == paint.getAlpha() ? '=' : '!');
#StdOut
255 == paint.getAlpha()
##
##
##
#Method void setAlpha(U8CPU a)
#In Alpha_Methods
#Line # sets Color_Alpha, color opacity ##
#Populate
#Example
SkPaint paint;
paint.setColor(0x00112233);
paint.setAlpha(0x44);
SkDebugf("0x44112233 %c= paint.getColor()\n", 0x44112233 == paint.getColor() ? '=' : '!');
#StdOut
0x44112233 == paint.getColor()
##
##
##
#Method void setARGB(U8CPU a, U8CPU r, U8CPU g, U8CPU b)
#In Color_Methods
#Line # sets color by component ##
#Populate
#Example
SkPaint transRed1, transRed2;
transRed1.setARGB(255 / 2, 255, 0, 0);
transRed2.setColor(SkColorSetARGB(255 / 2, 255, 0, 0));
SkDebugf("transRed1 %c= transRed2", transRed1 == transRed2 ? '=' : '!');
#StdOut
transRed1 == transRed2
##
##
#SeeAlso setColor SkColorSetARGB
##
# ------------------------------------------------------------------------------
#Subtopic Style
#Line # geometry filling, stroking ##
Style specifies if the geometry is filled, stroked, or both filled and stroked.
Some shapes ignore Style and are always drawn filled or stroked.
#Subtopic Fill
Set Style to kFill_Style to fill the shape.
The fill covers the area inside the geometry for most shapes.
#Subtopic Fill ##
#Subtopic Stroke
Set Style to kStroke_Style to stroke the shape.
The stroke covers the area described by following the shape edge with a pen or brush of
Stroke_Width. The area covered where the shape starts and stops is described by Stroke_Cap.
The area covered where the shape turns a corner is described by Stroke_Join.
The stroke is centered on the shape; it extends equally on either side of the shape edge.
#Subtopic Stroke ##
As Stroke_Width gets smaller, the drawn path frame is thinner. Stroke_Width less than one
may have gaps, and if kAntiAlias_Flag is set, Color_Alpha will increase to visually decrease coverage.
#SeeAlso Path_Fill_Type Path_Effect Style_Fill Style_Stroke
#Subtopic Style ##
#Subtopic Hairline
Stroke_Width of zero has a special meaning and switches drawing to use Hairline.
Hairline draws the thinnest continuous frame. If kAntiAlias_Flag is clear, adjacent pixels
flow horizontally, vertically,or diagonally.
#ToDo what is the description of Anti_Aliased hairlines? ##
Path drawing with Hairline may hit the same pixel more than once. For instance, Path containing
two lines in one Path_Contour will draw the corner point once, but may both lines may draw the adjacent
pixel. If kAntiAlias_Flag is set, transparency is applied twice, resulting in a darker pixel. Some
GPU-backed implementations apply transparency at a later drawing stage, avoiding double hit pixels
while stroking.
#SeeAlso Path_Fill_Type Path_Effect Style_Fill Style_Stroke
#Subtopic Hairline ##
#Enum Style
#Line # stroke, fill, or both ##
#Code
#Populate
##
#Code
#In Constant
#Filter kStyle
#Populate
##
Set Style to fill, stroke, or both fill and stroke geometry.
The stroke and fill
share all paint attributes; for instance, they are drawn with the same color.
Use kStrokeAndFill_Style to avoid hitting the same pixels twice with a stroke draw and
a fill draw.
#Const kFill_Style 0
#Line # set to fill geometry ##
Applies to Rect, Region, Round_Rect, Circles, Ovals, Path, and Text.
Bitmap, Image, Patches, Region, Sprites, and Vertices are painted as if
kFill_Style is set, and ignore the set Style.
The Path_Fill_Type specifies additional rules to fill the area outside the path edge,
and to create an unfilled hole inside the shape.
Style is set to kFill_Style by default.
##
#Const kStroke_Style 1
#Line # set to stroke geometry ##
Applies to Rect, Region, Round_Rect, Arcs, Circles, Ovals, Path, and Text.
Arcs, Lines, and points, are always drawn as if kStroke_Style is set,
and ignore the set Style.
The stroke construction is unaffected by the Path_Fill_Type.
##
#Const kStrokeAndFill_Style 2
#Line # sets to stroke and fill geometry ##
Applies to Rect, Region, Round_Rect, Circles, Ovals, Path, and Text.
Path is treated as if it is set to SkPath::kWinding_FillType,
and the set Path_Fill_Type is ignored.
##
#Const kStyleCount 3
#Line # number of different Style values defined ##
May be used to verify that Style is a legal value.
##
#Enum Style ##
#Method Style getStyle() const
#In Style
#Line # returns Style: stroke, fill, or both ##
#Populate
#Example
SkPaint paint;
SkDebugf("SkPaint::kFill_Style %c= paint.getStyle()\n",
SkPaint::kFill_Style == paint.getStyle() ? '=' : '!');
#StdOut
SkPaint::kFill_Style == paint.getStyle()
##
##
#SeeAlso Style setStyle
##
#Method void setStyle(Style style)
#In Style
#Line # sets Style: stroke, fill, or both ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setStrokeWidth(5);
SkRegion region;
region.op(140, 10, 160, 30, SkRegion::kUnion_Op);
region.op(170, 40, 190, 60, SkRegion::kUnion_Op);
SkBitmap bitmap;
bitmap.setInfo(SkImageInfo::MakeA8(50, 50), 50);
uint8_t pixels[50][50];
for (int x = 0; x < 50; ++x) {
for (int y = 0; y < 50; ++y) {
pixels[y][x] = (x + y) % 5 ? 0xFF : 0x00;
}
}
bitmap.setPixels(pixels);
for (auto style : { SkPaint::kFill_Style,
SkPaint::kStroke_Style,
SkPaint::kStrokeAndFill_Style }) {
paint.setStyle(style);
canvas->drawLine(10, 10, 60, 60, paint);
canvas->drawRect({80, 10, 130, 60}, paint);
canvas->drawRegion(region, paint);
canvas->drawBitmap(bitmap, 200, 10, &paint);
canvas->translate(0, 80);
}
}
##
#SeeAlso Style getStyle
##
# ------------------------------------------------------------------------------
#Subtopic Stroke_Width
#Line # thickness perpendicular to geometry ##
Stroke_Width sets the width for stroking. The width is the thickness
of the stroke perpendicular to the path direction when the paint style is
set to kStroke_Style or kStrokeAndFill_Style.
When width is greater than zero, the stroke encompasses as many pixels partially
or fully as needed. When the width equals zero, the paint enables hairlines;
the stroke is always one pixel wide.
The stroke dimensions are scaled by the canvas matrix, but Hairline stroke
remains one pixel wide regardless of scaling.
The default width for the paint is zero.
#Example
#Height 170
#Platform raster gpu
#Description
The pixels hit to represent thin lines vary with the angle of the
line and the platform implementation.
##
void draw(SkCanvas* canvas) {
SkPaint paint;
for (bool antialias : { false, true }) {
paint.setAntiAlias(antialias);
for (int width = 0; width <= 4; ++width) {
SkScalar offset = antialias * 100 + width * 20;
paint.setStrokeWidth(width * 0.25f);
canvas->drawLine(10 + offset, 10, 20 + offset, 60, paint);
canvas->drawLine(10 + offset, 110, 60 + offset, 160, paint);
}
}
}
##
#Method SkScalar getStrokeWidth() const
#In Stroke_Width
#Line # returns thickness of the stroke ##
#Populate
#Example
SkPaint paint;
SkDebugf("0 %c= paint.getStrokeWidth()\n", 0 == paint.getStrokeWidth() ? '=' : '!');
#StdOut
0 == paint.getStrokeWidth()
##
##
##
#Method void setStrokeWidth(SkScalar width)
#In Stroke_Width
#Line # sets thickness of the stroke ##
#Populate
#Example
SkPaint paint;
paint.setStrokeWidth(5);
paint.setStrokeWidth(-1);
SkDebugf("5 %c= paint.getStrokeWidth()\n", 5 == paint.getStrokeWidth() ? '=' : '!');
#StdOut
5 == paint.getStrokeWidth()
##
##
##
#Subtopic Stroke_Width ##
# ------------------------------------------------------------------------------
#Subtopic Miter_Limit
#Line # maximum length of stroked corners ##
Miter_Limit specifies the maximum miter length,
relative to the stroke width.
Miter_Limit is used when the Stroke_Join
is set to kMiter_Join, and the Style is either kStroke_Style
or kStrokeAndFill_Style.
If the miter at a corner exceeds this limit, kMiter_Join
is replaced with kBevel_Join.
Miter_Limit can be computed from the corner angle using:
#Formula # miter limit = 1 / sin ( angle / 2 ) ##.
Miter_Limit default value is 4.
The default may be changed at compile time by setting SkPaintDefaults_MiterLimit
in "SkUserConfig.h" or as a define supplied by the build environment.
Here are some miter limits and the angles that triggers them.
#Table
#Legend
# miter limit # angle in degrees ##
#Legend ##
# 10 # 11.48 ##
# 9 # 12.76 ##
# 8 # 14.36 ##
# 7 # 16.43 ##
# 6 # 19.19 ##
# 5 # 23.07 ##
# 4 # 28.96 ##
# 3 # 38.94 ##
# 2 # 60 ##
# 1 # 180 ##
#Table ##
#Example
#Height 170
#Width 384
#Description
This example draws a stroked corner and the miter length beneath.
When the miter limit is decreased slightly, the miter join is replaced
by a bevel join.
##
void draw(SkCanvas* canvas) {
SkPoint pts[] = {{ 10, 50 }, { 110, 80 }, { 10, 110 }};
SkVector v[] = { pts[0] - pts[1], pts[2] - pts[1] };
SkScalar angle1 = SkScalarATan2(v[0].fY, v[0].fX);
SkScalar angle2 = SkScalarATan2(v[1].fY, v[1].fX);
const SkScalar strokeWidth = 20;
SkScalar miterLimit = 1 / SkScalarSin((angle2 - angle1) / 2);
SkScalar miterLength = strokeWidth * miterLimit;
SkPath path;
path.moveTo(pts[0]);
path.lineTo(pts[1]);
path.lineTo(pts[2]);
SkPaint paint; // set to default kMiter_Join
paint.setAntiAlias(true);
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeMiter(miterLimit);
paint.setStrokeWidth(strokeWidth);
canvas->drawPath(path, paint);
paint.setStrokeWidth(1);
canvas->drawLine(pts[1].fX - miterLength / 2, pts[1].fY + 50,
pts[1].fX + miterLength / 2, pts[1].fY + 50, paint);
canvas->translate(200, 0);
miterLimit *= 0.99f;
paint.setStrokeMiter(miterLimit);
paint.setStrokeWidth(strokeWidth);
canvas->drawPath(path, paint);
paint.setStrokeWidth(1);
canvas->drawLine(pts[1].fX - miterLength / 2, pts[1].fY + 50,
pts[1].fX + miterLength / 2, pts[1].fY + 50, paint);
}
##
#Method SkScalar getStrokeMiter() const
#In Miter_Limit
#Line # returns Miter_Limit, angles with sharp corners ##
#Populate
#Example
SkPaint paint;
SkDebugf("default miter limit == %g\n", paint.getStrokeMiter());
#StdOut
default miter limit == 4
##
##
#SeeAlso Miter_Limit setStrokeMiter Join
##
#Method void setStrokeMiter(SkScalar miter)
#In Miter_Limit
#Line # sets Miter_Limit, angles with sharp corners ##
#Populate
#Example
SkPaint paint;
paint.setStrokeMiter(8);
paint.setStrokeMiter(-1);
SkDebugf("default miter limit == %g\n", paint.getStrokeMiter());
#StdOut
default miter limit == 8
##
##
#SeeAlso Miter_Limit getStrokeMiter Join
##
#Subtopic Miter_Limit ##
# ------------------------------------------------------------------------------
#Subtopic Stroke_Cap
#Line # decorations at ends of open strokes ##
#Subtopic Stroke_Cap ##
#Enum Cap
#Line # start and end geometry on stroked shapes ##
#Code
#Populate
##
#Code
#In Constant
#Filter kCap
#Populate
##
Stroke_Cap draws at the beginning and end of an open Path_Contour.
#Const kButt_Cap 0
#Line # no stroke extension ##
Does not extend the stroke past the beginning or the end.
##
#Const kRound_Cap 1
#Line # adds circle ##
Adds a circle with a diameter equal to Stroke_Width at the beginning
and end.
##
#Const kSquare_Cap 2
#Line # adds square ##
Adds a square with sides equal to Stroke_Width at the beginning
and end. The square sides are parallel to the initial and final direction
of the stroke.
##
#Const kLast_Cap 2
#Line # largest Stroke_Cap value ##
Equivalent to the largest value for Stroke_Cap.
##
#Const kDefault_Cap 0
#Line # equivalent to kButt_Cap ##
Stroke_Cap is set to kButt_Cap by default.
##
#Const kCapCount 3
#Line # number of different Stroke_Cap values defined ##
May be used to verify that Stroke_Cap is a legal value.
##
#Enum ##
Stroke describes the area covered by a pen of Stroke_Width as it
follows the Path_Contour, moving parallel to the contour direction.
If the Path_Contour is not terminated by SkPath::kClose_Verb, the contour has a
visible beginning and end.
Path_Contour may start and end at the same point; defining Zero_Length_Contour.
kButt_Cap and Zero_Length_Contour is not drawn.
kRound_Cap and Zero_Length_Contour draws a circle of diameter Stroke_Width
at the contour point.
kSquare_Cap and Zero_Length_Contour draws an upright square with a side of
Stroke_Width at the contour point.
Stroke_Cap is kButt_Cap by default.
#Example
#Height 200
SkPaint paint;
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(20);
SkPath path;
path.moveTo(30, 30);
path.lineTo(30, 30);
path.moveTo(70, 30);
path.lineTo(90, 40);
for (SkPaint::Cap c : { SkPaint::kButt_Cap, SkPaint::kRound_Cap, SkPaint::kSquare_Cap } ) {
paint.setStrokeCap(c);
canvas->drawPath(path, paint);
canvas->translate(0, 70);
}
##
#Method Cap getStrokeCap() const
#In Stroke_Cap
#Line # returns Cap, the area drawn at path ends ##
#Populate
#Example
SkPaint paint;
SkDebugf("kButt_Cap %c= default stroke cap\n",
SkPaint::kButt_Cap == paint.getStrokeCap() ? '=' : '!');
#StdOut
kButt_Cap == default stroke cap
##
##
#SeeAlso Stroke_Cap setStrokeCap
##
#Method void setStrokeCap(Cap cap)
#In Stroke_Cap
#Line # sets Cap, the area drawn at path ends ##
#Populate
#Example
SkPaint paint;
paint.setStrokeCap(SkPaint::kRound_Cap);
paint.setStrokeCap((SkPaint::Cap) SkPaint::kCapCount);
SkDebugf("kRound_Cap %c= paint.getStrokeCap()\n",
SkPaint::kRound_Cap == paint.getStrokeCap() ? '=' : '!');
#StdOut
kRound_Cap == paint.getStrokeCap()
##
##
#SeeAlso Stroke_Cap getStrokeCap
##
# ------------------------------------------------------------------------------
#Subtopic Stroke_Join
#Line # decoration at corners of strokes ##
#Subtopic Stroke_Join ##
Stroke_Join draws at the sharp corners of an open or closed Path_Contour.
Stroke describes the area covered by a pen of Stroke_Width as it
follows the Path_Contour, moving parallel to the contour direction.
If the contour direction changes abruptly, because the tangent direction leading
to the end of a curve within the contour does not match the tangent direction of
the following curve, the pair of curves meet at Stroke_Join.
#Example
#Height 200
SkPaint paint;
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(20);
SkPath path;
path.moveTo(30, 20);
path.lineTo(40, 40);
path.conicTo(70, 20, 100, 20, .707f);
for (SkPaint::Join j : { SkPaint::kMiter_Join, SkPaint::kRound_Join, SkPaint::kBevel_Join } ) {
paint.setStrokeJoin(j);
canvas->drawPath(path, paint);
canvas->translate(0, 70);
}
##
#Enum Join
#Line # corner geometry on stroked shapes ##
#Code
#Populate
##
#Code
#In Constant
#Filter kJoin
#Populate
##
Join specifies how corners are drawn when a shape is stroked. Join
affects the four corners of a stroked rectangle, and the connected segments in a
stroked path.
Choose miter join to draw sharp corners. Choose round join to draw a circle with a
radius equal to the stroke width on top of the corner. Choose bevel join to minimally
connect the thick strokes.
The fill path constructed to describe the stroked path respects the join setting but may
not contain the actual join. For instance, a fill path constructed with round joins does
not necessarily include circles at each connected segment.
#Const kMiter_Join 0
#Line # extends to Miter_Limit ##
Extends the outside corner to the extent allowed by Miter_Limit.
If the extension exceeds Miter_Limit, kBevel_Join is used instead.
##
#Const kRound_Join 1
#Line # adds circle ##
Adds a circle with a diameter of Stroke_Width at the sharp corner.
##
#Const kBevel_Join 2
#Line # connects outside edges ##
Connects the outside edges of the sharp corner.
##
#Const kLast_Join 2
#Line # equivalent to the largest value for Stroke_Join ##
##
#Const kDefault_Join 1
#Line # equivalent to kMiter_Join ##
Stroke_Join is set to kMiter_Join by default.
##
#Const kJoinCount 3
#Line # number of different Stroke_Join values defined ##
May be used to verify that Stroke_Join is a legal value.
##
#Example
#Width 462
void draw(SkCanvas* canvas) {
SkPath path;
path.moveTo(10, 50);
path.quadTo(35, 110, 60, 210);
path.quadTo(105, 110, 130, 10);
SkPaint paint; // set to default kMiter_Join
paint.setAntiAlias(true);
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(20);
canvas->drawPath(path, paint);
canvas->translate(150, 0);
paint.setStrokeJoin(SkPaint::kBevel_Join);
canvas->drawPath(path, paint);
canvas->translate(150, 0);
paint.setStrokeJoin(SkPaint::kRound_Join);
canvas->drawPath(path, paint);
}
##
#SeeAlso setStrokeJoin getStrokeJoin setStrokeMiter getStrokeMiter
#Enum ##
#Method Join getStrokeJoin() const
#In Stroke_Join
#Line # returns Join, geometry on path corners ##
#Populate
#Example
SkPaint paint;
SkDebugf("kMiter_Join %c= default stroke join\n",
SkPaint::kMiter_Join == paint.getStrokeJoin() ? '=' : '!');
#StdOut
kMiter_Join == default stroke join
##
##
#SeeAlso Stroke_Join setStrokeJoin
##
#Method void setStrokeJoin(Join join)
#In Stroke_Join
#Line # sets Join, geometry on path corners ##
#Populate
#Example
SkPaint paint;
paint.setStrokeJoin(SkPaint::kMiter_Join);
paint.setStrokeJoin((SkPaint::Join) SkPaint::kJoinCount);
SkDebugf("kMiter_Join %c= paint.getStrokeJoin()\n",
SkPaint::kMiter_Join == paint.getStrokeJoin() ? '=' : '!');
#StdOut
kMiter_Join == paint.getStrokeJoin()
##
##
#SeeAlso Stroke_Join getStrokeJoin
##
#SeeAlso Miter_Limit
# ------------------------------------------------------------------------------
#Subtopic Fill_Path
#Line # make Path from Path_Effect, stroking ##
Fill_Path creates a Path by applying the Path_Effect, followed by the Style_Stroke.
If Paint contains Path_Effect, Path_Effect operates on the source Path; the result
replaces the destination Path. Otherwise, the source Path is replaces the
destination Path.
Fill Path can request the Path_Effect to restrict to a culling rectangle, but
the Path_Effect is not required to do so.
If Style is kStroke_Style or kStrokeAndFill_Style,
and Stroke_Width is greater than zero, the Stroke_Width, Stroke_Cap, Stroke_Join,
and Miter_Limit operate on the destination Path, replacing it.
Fill Path can specify the precision used by Stroke_Width to approximate the stroke geometry.
If the Style is kStroke_Style and the Stroke_Width is zero, getFillPath
returns false since Hairline has no filled equivalent.
#SeeAlso Style_Stroke Stroke_Width Path_Effect
#Subtopic Fill_Path ##
#Method bool getFillPath(const SkPath& src, SkPath* dst, const SkRect* cullRect,
SkScalar resScale = 1) const
#In Fill_Path
#Line # returns fill path equivalent to stroke ##
#Populate
#Example
#Height 192
#Description
A very small Quad stroke is turned into a filled path with increasing levels of precision.
At the lowest precision, the Quad stroke is approximated by a rectangle.
At the highest precision, the filled path has high fidelity compared to the original stroke.
##
void draw(SkCanvas* canvas) {
SkPaint strokePaint;
strokePaint.setAntiAlias(true);
strokePaint.setStyle(SkPaint::kStroke_Style);
strokePaint.setStrokeWidth(.1f);
SkPath strokePath;
strokePath.moveTo(.08f, .08f);
strokePath.quadTo(.09f, .08f, .17f, .17f);
SkPath fillPath;
SkPaint outlinePaint(strokePaint);
outlinePaint.setStrokeWidth(2);
SkMatrix scale = SkMatrix::MakeScale(300, 300);
for (SkScalar precision : { 0.01f, .1f, 1.f, 10.f, 100.f } ) {
strokePaint.getFillPath(strokePath, &fillPath, nullptr, precision);
fillPath.transform(scale);
canvas->drawPath(fillPath, outlinePaint);
canvas->translate(60, 0);
if (1.f == precision) canvas->translate(-180, 100);
}
strokePath.transform(scale);
strokePaint.setStrokeWidth(30);
canvas->drawPath(strokePath, strokePaint);
}
##
##
#Method bool getFillPath(const SkPath& src, SkPath* dst) const
#In Fill_Path
#Populate
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(10);
SkPath strokePath;
strokePath.moveTo(20, 20);
strokePath.lineTo(100, 100);
canvas->drawPath(strokePath, paint);
SkPath fillPath;
paint.getFillPath(strokePath, &fillPath);
paint.setStrokeWidth(2);
canvas->translate(40, 0);
canvas->drawPath(fillPath, paint);
}
##
##
# ------------------------------------------------------------------------------
#Subtopic Shader_Methods
#Line # get and set Shader ##
Shader defines the colors used when drawing a shape.
Shader may be an image, a gradient, or a computed fill.
If Paint has no Shader, then Color fills the shape.
Shader is modulated by Color_Alpha component of Color.
If Shader object defines only Color_Alpha, then Color modulated by Color_Alpha describes
the fill.
The drawn transparency can be modified without altering Shader, by changing Color_Alpha.
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkPoint center = { 50, 50 };
SkScalar radius = 50;
const SkColor colors[] = { 0xFFFFFFFF, 0xFF000000 };
paint.setShader(SkGradientShader::MakeRadial(center, radius, colors,
nullptr, SK_ARRAY_COUNT(colors), SkShader::kClamp_TileMode));
for (SkScalar a : { 0.3f, 0.6f, 1.0f } ) {
paint.setAlpha((int) (a * 255));
canvas->drawCircle(center.fX, center.fY, radius, paint);
canvas->translate(70, 70);
}
}
##
If Shader generates only Color_Alpha then all components of Color modulate the output.
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkBitmap bitmap;
bitmap.setInfo(SkImageInfo::MakeA8(5, 1), 5); // bitmap only contains alpha
uint8_t pixels[5] = { 0x22, 0x55, 0x88, 0xBB, 0xFF };
bitmap.setPixels(pixels);
paint.setShader(SkShader::MakeBitmapShader(bitmap,
SkShader::kMirror_TileMode, SkShader::kMirror_TileMode));
for (SkColor c : { SK_ColorRED, SK_ColorBLUE, SK_ColorGREEN } ) {
paint.setColor(c); // all components in color affect shader
canvas->drawCircle(50, 50, 50, paint);
canvas->translate(70, 70);
}
}
##
#Method SkShader* getShader() const
#In Shader_Methods
#Line # returns Shader, multiple drawing colors; gradients ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("nullptr %c= shader\n", paint.getShader() ? '!' : '=');
paint.setShader(SkShader::MakeEmptyShader());
SkDebugf("nullptr %c= shader\n", paint.getShader() ? '!' : '=');
}
#StdOut
nullptr == shader
nullptr != shader
##
##
##
#Method sk_sp<SkShader> refShader() const
#In Shader_Methods
#Line # references Shader, multiple drawing colors; gradients ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint1, paint2;
paint1.setShader(SkShader::MakeEmptyShader());
SkDebugf("shader unique: %s\n", paint1.getShader()->unique() ? "true" : "false");
paint2.setShader(paint1.refShader());
SkDebugf("shader unique: %s\n", paint1.getShader()->unique() ? "true" : "false");
}
#StdOut
shader unique: true
shader unique: false
##
##
##
#Method void setShader(sk_sp<SkShader> shader)
#In Shader_Methods
#Line # sets Shader, multiple drawing colors; gradients ##
#Populate
#Example
#Height 64
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setColor(SK_ColorBLUE);
paint.setShader(SkShader::MakeColorShader(SK_ColorRED));
canvas->drawRect(SkRect::MakeWH(40, 40), paint);
paint.setShader(nullptr);
canvas->translate(50, 0);
canvas->drawRect(SkRect::MakeWH(40, 40), paint);
}
##
##
#Subtopic Shader_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Color_Filter_Methods
#Line # get and set Color_Filter ##
Color_Filter alters the color used when drawing a shape.
Color_Filter may apply Blend_Mode, transform the color through a matrix, or composite multiple filters.
If Paint has no Color_Filter, the color is unaltered.
The drawn transparency can be modified without altering Color_Filter, by changing Color_Alpha.
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setColorFilter(SkColorMatrixFilter::MakeLightingFilter(0xFFFFFF, 0xFF0000));
for (SkColor c : { SK_ColorBLACK, SK_ColorGREEN } ) {
paint.setColor(c);
canvas->drawRect(SkRect::MakeXYWH(10, 10, 50, 50), paint);
paint.setAlpha(0x80);
canvas->drawRect(SkRect::MakeXYWH(60, 60, 50, 50), paint);
canvas->translate(100, 0);
}
}
##
#Method SkColorFilter* getColorFilter() const
#In Color_Filter_Methods
#Line # returns Color_Filter, how colors are altered ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("nullptr %c= color filter\n", paint.getColorFilter() ? '!' : '=');
paint.setColorFilter(SkColorFilter::MakeModeFilter(SK_ColorLTGRAY, SkBlendMode::kSrcIn));
SkDebugf("nullptr %c= color filter\n", paint.getColorFilter() ? '!' : '=');
}
#StdOut
nullptr == color filter
nullptr != color filter
##
##
##
#Method sk_sp<SkColorFilter> refColorFilter() const
#In Color_Filter_Methods
#Line # references Color_Filter, how colors are altered ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint1, paint2;
paint1.setColorFilter(SkColorFilter::MakeModeFilter(0xFFFF0000, SkBlendMode::kSrcATop));
SkDebugf("color filter unique: %s\n", paint1.getColorFilter()->unique() ? "true" : "false");
paint2.setColorFilter(paint1.refColorFilter());
SkDebugf("color filter unique: %s\n", paint1.getColorFilter()->unique() ? "true" : "false");
}
#StdOut
color filter unique: true
color filter unique: false
##
##
##
#Method void setColorFilter(sk_sp<SkColorFilter> colorFilter)
#In Color_Filter_Methods
#Line # sets Color_Filter, alters color ##
#Populate
#Example
#Height 64
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setColorFilter(SkColorFilter::MakeModeFilter(SK_ColorLTGRAY, SkBlendMode::kSrcIn));
canvas->drawRect(SkRect::MakeWH(50, 50), paint);
paint.setColorFilter(nullptr);
canvas->translate(70, 0);
canvas->drawRect(SkRect::MakeWH(50, 50), paint);
}
##
##
#Subtopic Color_Filter_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Blend_Mode_Methods
#Line # get and set Blend_Mode ##
Blend_Mode describes how Color combines with the destination color.
The default setting, SkBlendMode::kSrcOver, draws the source color
over the destination color.
#Example
void draw(SkCanvas* canvas) {
SkPaint normal, blender;
normal.setColor(0xFF58a889);
blender.setColor(0xFF8958a8);
canvas->clear(0);
for (SkBlendMode m : { SkBlendMode::kSrcOver, SkBlendMode::kSrcIn, SkBlendMode::kSrcOut } ) {
normal.setBlendMode(SkBlendMode::kSrcOver);
canvas->drawOval(SkRect::MakeXYWH(30, 30, 30, 80), normal);
blender.setBlendMode(m);
canvas->drawOval(SkRect::MakeXYWH(10, 50, 80, 30), blender);
canvas->translate(70, 70);
}
}
##
#SeeAlso Blend_Mode
#Method SkBlendMode getBlendMode() const
#In Blend_Mode_Methods
#Line # returns Blend_Mode, how colors combine with Device ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("kSrcOver %c= getBlendMode\n",
SkBlendMode::kSrcOver == paint.getBlendMode() ? '=' : '!');
paint.setBlendMode(SkBlendMode::kSrc);
SkDebugf("kSrcOver %c= getBlendMode\n",
SkBlendMode::kSrcOver == paint.getBlendMode() ? '=' : '!');
}
#StdOut
kSrcOver == getBlendMode
kSrcOver != getBlendMode
##
##
##
#Method bool isSrcOver() const
#In Blend_Mode_Methods
#Line # returns true if Blend_Mode is SkBlendMode::kSrcOver ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("isSrcOver %c= true\n", paint.isSrcOver() ? '=' : '!');
paint.setBlendMode(SkBlendMode::kSrc);
SkDebugf("isSrcOver %c= true\n", paint.isSrcOver() ? '=' : '!');
}
#StdOut
isSrcOver == true
isSrcOver != true
##
##
##
#Method void setBlendMode(SkBlendMode mode)
#In Blend_Mode_Methods
#Line # sets Blend_Mode, how colors combine with destination ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("isSrcOver %c= true\n", paint.isSrcOver() ? '=' : '!');
paint.setBlendMode(SkBlendMode::kSrc);
SkDebugf("isSrcOver %c= true\n", paint.isSrcOver() ? '=' : '!');
}
#StdOut
isSrcOver == true
isSrcOver != true
##
##
##
#Subtopic Blend_Mode_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Path_Effect_Methods
#Line # get and set Path_Effect ##
Path_Effect modifies the path geometry before drawing it.
Path_Effect may implement dashing, custom fill effects and custom stroke effects.
If Paint has no Path_Effect, the path geometry is unaltered when filled or stroked.
#Example
#Height 160
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(16);
SkScalar intervals[] = {30, 10};
paint.setPathEffect(SkDashPathEffect::Make(intervals, SK_ARRAY_COUNT(intervals), 1));
canvas->drawRoundRect({20, 20, 120, 120}, 20, 20, paint);
}
##
#SeeAlso Path_Effect
#Method SkPathEffect* getPathEffect() const
#In Path_Effect_Methods
#Line # returns Path_Effect, modifications to path geometry; dashing ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("nullptr %c= path effect\n", paint.getPathEffect() ? '!' : '=');
paint.setPathEffect(SkCornerPathEffect::Make(10));
SkDebugf("nullptr %c= path effect\n", paint.getPathEffect() ? '!' : '=');
}
#StdOut
nullptr == path effect
nullptr != path effect
##
##
##
#Method sk_sp<SkPathEffect> refPathEffect() const
#In Path_Effect_Methods
#Line # references Path_Effect, modifications to path geometry; dashing ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint1, paint2;
SkScalar intervals[] = {1, 2};
paint1.setPathEffect(SkDashPathEffect::Make(intervals, SK_ARRAY_COUNT(intervals), 10));
SkDebugf("path effect unique: %s\n", paint1.getPathEffect()->unique() ? "true" : "false");
paint2.setPathEffect(paint1.refPathEffect());
SkDebugf("path effect unique: %s\n", paint1.getPathEffect()->unique() ? "true" : "false");
}
#StdOut
path effect unique: true
path effect unique: false
##
##
##
#Method void setPathEffect(sk_sp<SkPathEffect> pathEffect)
#In Path_Effect_Methods
#Line # sets Path_Effect, modifications to path geometry; dashing ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setPathEffect(SkDiscretePathEffect::Make(3, 5));
canvas->drawRect(SkRect::MakeXYWH(40, 40, 175, 175), paint);
}
##
##
#Subtopic Path_Effect_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Mask_Filter_Methods
#Line # get and set Mask_Filter ##
Mask_Filter uses coverage of the shape drawn to create Mask_Alpha.
Mask_Filter takes a Mask, and returns a Mask.
Mask_Filter may change the geometry and transparency of the shape, such as
creating a blur effect. Set Mask_Filter to nullptr to prevent Mask_Filter from
modifying the draw.
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setMaskFilter(SkMaskFilter::MakeBlur(kSolid_SkBlurStyle, 3));
canvas->drawRect(SkRect::MakeXYWH(40, 40, 175, 175), paint);
}
##
#Method SkMaskFilter* getMaskFilter() const
#In Mask_Filter_Methods
#Line # returns Mask_Filter, alterations to Mask_Alpha ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("nullptr %c= mask filter\n", paint.getMaskFilter() ? '!' : '=');
paint.setMaskFilter(SkMaskFilter::MakeBlur(kOuter_SkBlurStyle, 3));
SkDebugf("nullptr %c= mask filter\n", paint.getMaskFilter() ? '!' : '=');
}
#StdOut
nullptr == mask filter
nullptr != mask filter
##
##
##
#Method sk_sp<SkMaskFilter> refMaskFilter() const
#In Mask_Filter_Methods
#Line # references Mask_Filter, alterations to Mask_Alpha ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint1, paint2;
paint1.setMaskFilter(SkMaskFilter::MakeBlur(kNormal_SkBlurStyle, 1));
SkDebugf("mask filter unique: %s\n", paint1.getMaskFilter()->unique() ? "true" : "false");
paint2.setMaskFilter(paint1.refMaskFilter());
SkDebugf("mask filter unique: %s\n", paint1.getMaskFilter()->unique() ? "true" : "false");
}
#StdOut
mask filter unique: true
mask filter unique: false
##
##
##
#Method void setMaskFilter(sk_sp<SkMaskFilter> maskFilter)
#In Mask_Filter_Methods
#Line # sets Mask_Filter, alterations to Mask_Alpha ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(10);
paint.setMaskFilter(SkMaskFilter::MakeBlur(kNormal_SkBlurStyle, 10));
canvas->drawRect(SkRect::MakeXYWH(40, 40, 175, 175), paint);
}
##
##
#Subtopic Mask_Filter_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Typeface_Methods
#Line # get and set Typeface ##
Typeface identifies the font used when drawing and measuring text.
Typeface may be specified by name, from a file, or from a data stream.
The default Typeface defers to the platform-specific default font
implementation.
#Example
#Height 100
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setTypeface(SkTypeface::MakeFromName(nullptr, SkFontStyle()));
paint.setAntiAlias(true);
paint.setTextSize(36);
canvas->drawString("A Big Hello!", 10, 40, paint);
paint.setTypeface(nullptr);
paint.setFakeBoldText(true);
canvas->drawString("A Big Hello!", 10, 80, paint);
}
##
#Method SkTypeface* getTypeface() const
#In Typeface_Methods
#Line # returns Typeface, font description ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("nullptr %c= typeface\n", paint.getTypeface() ? '!' : '=');
paint.setTypeface(SkTypeface::MakeFromName("monospace", SkFontStyle()));
SkDebugf("nullptr %c= typeface\n", paint.getTypeface() ? '!' : '=');
}
#StdOut
nullptr == typeface
nullptr != typeface
##
##
##
#Method sk_sp<SkTypeface> refTypeface() const
#In Typeface_Methods
#Line # references Typeface, font description ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint1, paint2;
paint1.setTypeface(SkTypeface::MakeFromName("monospace",
SkFontStyle(SkFontStyle::kNormal_Weight, SkFontStyle::kNormal_Width,
SkFontStyle::kItalic_Slant)));
SkDebugf("typeface1 %c= typeface2\n",
paint1.getTypeface() == paint2.getTypeface() ? '=' : '!');
paint2.setTypeface(paint1.refTypeface());
SkDebugf("typeface1 %c= typeface2\n",
paint1.getTypeface() == paint2.getTypeface() ? '=' : '!');
}
#StdOut
typeface1 != typeface2
typeface1 == typeface2
##
##
##
#Method void setTypeface(sk_sp<SkTypeface> typeface)
#In Typeface_Methods
#Line # sets Typeface, font description ##
#Populate
#Example
#Height 64
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setTypeface(SkTypeface::MakeFromName("monospace", SkFontStyle()));
canvas->drawString("hamburgerfons", 10, 30, paint);
paint.setTypeface(nullptr);
canvas->drawString("hamburgerfons", 10, 50, paint);
}
##
##
#Subtopic Typeface_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Image_Filter_Methods
#Line # get and set Image_Filter ##
Image_Filter operates on the pixel representation of the shape, as modified by Paint
with Blend_Mode set to SkBlendMode::kSrcOver. Image_Filter creates a new bitmap,
which is drawn to the device using the set Blend_Mode.
Image_Filter is higher level than Mask_Filter; for instance, an Image_Filter
can operate on all channels of Color, while Mask_Filter generates Alpha only.
Image_Filter operates independently of and can be used in combination with
Mask_Filter.
#Example
#ToDo explain why the two draws are so different ##
#Function
###$
#include "SkBlurImageFilter.h"
$$$#
##
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(2);
SkRegion region;
region.op( 10, 10, 50, 50, SkRegion::kUnion_Op);
region.op( 10, 50, 90, 90, SkRegion::kUnion_Op);
paint.setImageFilter(SkBlurImageFilter::Make(5.0f, 5.0f, nullptr));
canvas->drawRegion(region, paint);
paint.setImageFilter(nullptr);
paint.setMaskFilter(SkMaskFilter::MakeBlur(kNormal_SkBlurStyle, 5));
canvas->translate(100, 100);
canvas->drawRegion(region, paint);
}
##
#Method SkImageFilter* getImageFilter() const
#In Image_Filter_Methods
#Line # returns Image_Filter, alter pixels; blur ##
#Populate
#Example
#Function
###$
#include "SkBlurImageFilter.h"
$$$#
##
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("nullptr %c= image filter\n", paint.getImageFilter() ? '!' : '=');
paint.setImageFilter(SkBlurImageFilter::Make(kOuter_SkBlurStyle, 3, nullptr, nullptr));
SkDebugf("nullptr %c= image filter\n", paint.getImageFilter() ? '!' : '=');
}
#StdOut
nullptr == image filter
nullptr != image filter
##
##
##
#Method sk_sp<SkImageFilter> refImageFilter() const
#In Image_Filter_Methods
#Line # references Image_Filter, alter pixels; blur ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint1, paint2;
paint1.setImageFilter(SkOffsetImageFilter::Make(25, 25, nullptr));
SkDebugf("image filter unique: %s\n", paint1.getImageFilter()->unique() ? "true" : "false");
paint2.setImageFilter(paint1.refImageFilter());
SkDebugf("image filter unique: %s\n", paint1.getImageFilter()->unique() ? "true" : "false");
}
#StdOut
image filter unique: true
image filter unique: false
##
##
##
#Method void setImageFilter(sk_sp<SkImageFilter> imageFilter)
#In Image_Filter_Methods
#Line # sets Image_Filter, alter pixels; blur ##
#Populate
#Example
#Height 160
void draw(SkCanvas* canvas) {
SkBitmap bitmap;
bitmap.allocN32Pixels(100, 100);
SkCanvas offscreen(bitmap);
SkPaint paint;
paint.setAntiAlias(true);
paint.setColor(SK_ColorWHITE);
paint.setTextSize(96);
offscreen.clear(0);
offscreen.drawString("e", 20, 70, paint);
paint.setImageFilter(
SkLightingImageFilter::MakePointLitDiffuse(SkPoint3::Make(80, 100, 10),
SK_ColorWHITE, 1, 2, nullptr, nullptr));
canvas->drawBitmap(bitmap, 0, 0, &paint);
}
##
##
#Subtopic Image_Filter_Methods ##
# ------------------------------------------------------------------------------
#Subtopic Draw_Looper_Methods
#Line # get and set Draw_Looper ##
Draw_Looper sets a modifier that communicates state from one Draw_Layer
to another to construct the draw.
Draw_Looper draws one or more times, modifying the canvas and paint each time.
Draw_Looper may be used to draw multiple colors or create a colored shadow.
Set Draw_Looper to nullptr to prevent Draw_Looper from modifying the draw.
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkLayerDrawLooper::LayerInfo info;
info.fPaintBits = (SkLayerDrawLooper::BitFlags) SkLayerDrawLooper::kColorFilter_Bit;
info.fColorMode = SkBlendMode::kSrc;
SkLayerDrawLooper::Builder looperBuilder;
SkPaint* loopPaint = looperBuilder.addLayer(info);
loopPaint->setColor(SK_ColorRED);
info.fOffset.set(20, 20);
loopPaint = looperBuilder.addLayer(info);
loopPaint->setColor(SK_ColorBLUE);
SkPaint paint;
paint.setDrawLooper(looperBuilder.detach());
canvas->drawCircle(50, 50, 50, paint);
}
##
#Method SkDrawLooper* getDrawLooper() const
#In Draw_Looper_Methods
#Line # returns Draw_Looper, multiple layers ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint;
SkDebugf("nullptr %c= draw looper\n", paint.getDrawLooper() ? '!' : '=');
SkLayerDrawLooper::Builder looperBuilder;
paint.setDrawLooper(looperBuilder.detach());
SkDebugf("nullptr %c= draw looper\n", paint.getDrawLooper() ? '!' : '=');
}
#StdOut
nullptr == draw looper
nullptr != draw looper
##
##
##
#Method sk_sp<SkDrawLooper> refDrawLooper() const
#In Draw_Looper_Methods
#Line # references Draw_Looper, multiple layers ##
#Populate
#Example
void draw(SkCanvas* canvas) {
SkPaint paint1, paint2;
SkLayerDrawLooper::Builder looperBuilder;
paint1.setDrawLooper(looperBuilder.detach());
SkDebugf("draw looper unique: %s\n", paint1.getDrawLooper()->unique() ? "true" : "false");
paint2.setDrawLooper(paint1.refDrawLooper());
SkDebugf("draw looper unique: %s\n", paint1.getDrawLooper()->unique() ? "true" : "false");
}
#StdOut
draw looper unique: true
draw looper unique: false
##
##
##
#Method SkDrawLooper* getLooper() const
#Bug 6259
#Deprecated
##
#Method void setDrawLooper(sk_sp<SkDrawLooper> drawLooper)
#In Draw_Looper_Methods
#Line # sets Draw_Looper, multiple layers ##
#Populate
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setDrawLooper(SkBlurDrawLooper::Make(0x7FFF0000, 4, -5, -10));
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(10);
paint.setAntiAlias(true);
paint.setColor(0x7f0000ff);
canvas->drawCircle(70, 70, 50, paint);
}
##
##
#Method void setLooper(sk_sp<SkDrawLooper> drawLooper)
#Bug 6259
#Deprecated
##
#Subtopic Draw_Looper_Methods ##
#Subtopic Text_Size
#Line # overall height in points ##
Text_Size adjusts the overall text size in points.
Text_Size can be set to any positive value or zero.
Text_Size defaults to 12.
Set SkPaintDefaults_TextSize at compile time to change the default setting.
#Example
#Height 135
void draw(SkCanvas* canvas) {
SkPaint paint;
canvas->drawString("12 point", 10, 20, paint);
paint.setTextSize(24);
canvas->drawString("24 point", 10, 60, paint);
paint.setTextSize(48);
canvas->drawString("48 point", 10, 120, paint);
}
##
#Method SkScalar getTextSize() const
#In Text_Size
#Line # returns text size in points ##
#Populate
#Example
SkPaint paint;
SkDebugf("12 %c= default text size\n", 12 == paint.getTextSize() ? '=' : '!');
##
##
#Method void setTextSize(SkScalar textSize)
#In Text_Size
#Line # sets text size in points ##
#Populate
#Example
SkPaint paint;
SkDebugf("12 %c= text size\n", 12 == paint.getTextSize() ? '=' : '!');
paint.setTextSize(-20);
SkDebugf("12 %c= text size\n", 12 == paint.getTextSize() ? '=' : '!');
##
##
#Subtopic Text_Size ##
# ------------------------------------------------------------------------------
#Subtopic Text_Scale_X
#Line # text horizontal scale ##
Text_Scale_X adjusts the text horizontal scale.
Text scaling approximates condensed and expanded type faces when the actual face
is not available.
Text_Scale_X can be set to any value.
Text_Scale_X defaults to 1.
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
paint.setTextScaleX(.8f);
canvas->drawString("narrow", 10, 20, paint);
paint.setTextScaleX(1);
canvas->drawString("normal", 10, 60, paint);
paint.setTextScaleX(1.2f);
canvas->drawString("wide", 10, 100, paint);
}
##
#Method SkScalar getTextScaleX() const
#In Text_Scale_X
#Line # returns the text horizontal scale; condensed text ##
#Populate
#Example
SkPaint paint;
SkDebugf("1 %c= default text scale x\n", 1 == paint.getTextScaleX() ? '=' : '!');
##
##
#Method void setTextScaleX(SkScalar scaleX)
#In Text_Scale_X
#Line # sets the text horizontal scale; condensed text ##
#Populate
#Example
SkPaint paint;
paint.setTextScaleX(0.f / 0.f);
SkDebugf("text scale %s-a-number\n", SkScalarIsNaN(paint.getTextScaleX()) ? "not" : "is");
##
##
#Subtopic Text_Scale_X ##
#Subtopic Text_Skew_X
#Line # text horizontal slant ##
Text_Skew_X adjusts the text horizontal slant.
Text skewing approximates italic and oblique type faces when the actual face
is not available.
Text_Skew_X can be set to any value.
Text_Skew_X defaults to 0.
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(24);
paint.setTextSkewX(-.25f);
canvas->drawString("right-leaning", 10, 100, paint);
paint.setTextSkewX(0);
canvas->drawString("normal", 10, 60, paint);
paint.setTextSkewX(.25f);
canvas->drawString("left-leaning", 10, 20, paint);
}
##
#Method SkScalar getTextSkewX() const
#In Text_Skew_X
#Line # returns the text horizontal skew; oblique text ##
#Populate
#Example
SkPaint paint;
SkDebugf("0 %c= default text skew x\n", 0 == paint.getTextSkewX() ? '=' : '!');
##
##
#Method void setTextSkewX(SkScalar skewX)
#In Text_Skew_X
#Line # sets the text horizontal skew; oblique text ##
#Populate
#Example
SkPaint paint;
paint.setTextScaleX(1.f / 0.f);
SkDebugf("text scale %s-finite\n", SkScalarIsFinite(paint.getTextScaleX()) ? "is" : "not");
##
##
#Subtopic Text_Skew_X ##
# ------------------------------------------------------------------------------
#Subtopic Text_Encoding
#Line # text encoded as characters or Glyphs ##
#Enum TextEncoding
#Line # character or glyph encoded size ##
#Code
#Populate
##
TextEncoding determines whether text specifies character codes and their encoded
size, or glyph indices. Characters are encoded as specified by the
#A Unicode standard # https://unicode.org/standard/standard.html ##
.
Character codes encoded size are specified by UTF-8, UTF-16, or UTF-32.
All character code formats are able to represent all of Unicode, differing only
in the total storage required.
#A UTF-8 (RFC 3629) # https://tools.ietf.org/html/rfc3629 ##
encodes each character as one or more 8-bit bytes.
#A UTF-16 (RFC 2781) # https://tools.ietf.org/html/rfc2781 ##
encodes each character as one or two 16-bit words.
#A UTF-32 # https://www.unicode.org/versions/Unicode5.0.0/ch03.pdf ##
encodes each character as one 32-bit word.
Font_Manager uses font data to convert character code points into glyph indices.
A glyph index is a 16-bit word.
TextEncoding is set to kUTF8_TextEncoding by default.
#Const kUTF8_TextEncoding 0
#Line # uses bytes to represent UTF-8 or ASCII ##
##
#Const kUTF16_TextEncoding 1
#Line # uses two byte words to represent most of Unicode ##
##
#Const kUTF32_TextEncoding 2
#Line # uses four byte words to represent all of Unicode ##
##
#Const kGlyphID_TextEncoding 3
#Line # uses two byte words to represent glyph indices ##
##
#Enum ##
#Example
#Height 128
#Description
First line is encoded in UTF-8.
Second line is encoded in UTF-16.
Third line is encoded in UTF-32.
Fourth line has 16-bit glyph indices.
##
void draw(SkCanvas* canvas) {
SkPaint paint;
const char hello8[] = "Hello" "\xE2" "\x98" "\xBA";
const uint16_t hello16[] = { 'H', 'e', 'l', 'l', 'o', 0x263A };
const uint32_t hello32[] = { 'H', 'e', 'l', 'l', 'o', 0x263A };
paint.setTextSize(24);
canvas->drawText(hello8, sizeof(hello8) - 1, 10, 30, paint);
paint.setTextEncoding(SkPaint::kUTF16_TextEncoding);
canvas->drawText(hello16, sizeof(hello16), 10, 60, paint);
paint.setTextEncoding(SkPaint::kUTF32_TextEncoding);
canvas->drawText(hello32, sizeof(hello32), 10, 90, paint);
uint16_t glyphs[SK_ARRAY_COUNT(hello32)];
paint.textToGlyphs(hello32, sizeof(hello32), glyphs);
paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
canvas->drawText(glyphs, sizeof(glyphs), 10, 120, paint);
}
##
#Method TextEncoding getTextEncoding() const
#In Text_Encoding
#Line # returns character or glyph encoded size ##
#Populate
#Example
SkPaint paint;
SkDebugf("kUTF8_TextEncoding %c= text encoding\n",
SkPaint::kUTF8_TextEncoding == paint.getTextEncoding() ? '=' : '!');
paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
SkDebugf("kGlyphID_TextEncoding %c= text encoding\n",
SkPaint::kGlyphID_TextEncoding == paint.getTextEncoding() ? '=' : '!');
#StdOut
kUTF8_TextEncoding == text encoding
kGlyphID_TextEncoding == text encoding
##
##
##
#Method void setTextEncoding(TextEncoding encoding)
#In Text_Encoding
#Line # sets character or glyph encoded size ##
#Populate
#Example
SkPaint paint;
paint.setTextEncoding((SkPaint::TextEncoding) 4);
SkDebugf("4 %c= text encoding\n", (SkPaint::TextEncoding) 4 == paint.getTextEncoding() ? '=' : '!');
#StdOut
4 != text encoding
##
##
##
#Typedef typedef SkFontMetrics FontMetrics
##
#Subtopic Text_Encoding ##
# ------------------------------------------------------------------------------
#Subtopic Font_Metrics
#Method SkScalar getFontMetrics(SkFontMetrics* metrics) const
#In Font_Metrics
#Line # returns Typeface metrics scaled by text size ##
#Populate
#Example
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setTextSize(32);
SkScalar lineHeight = paint.getFontMetrics(nullptr);
canvas->drawString("line 1", 10, 40, paint);
canvas->drawString("line 2", 10, 40 + lineHeight, paint);
}
##
#SeeAlso Text_Size Typeface Typeface_Methods
##
#Method SkScalar getFontSpacing() const
#In Font_Metrics
#Line # returns recommended spacing between lines ##
#Populate
#Example
SkPaint paint;
for (SkScalar textSize : { 12, 18, 24, 32 } ) {
paint.setTextSize(textSize);
SkDebugf("textSize: %g fontSpacing: %g\n", textSize, paint.getFontSpacing());
}
#StdOut
textSize: 12 fontSpacing: 13.9688
textSize: 18 fontSpacing: 20.9531
textSize: 24 fontSpacing: 27.9375
textSize: 32 fontSpacing: 37.25
##
##
##
#Method SkRect getFontBounds() const
#In Font_Metrics
#Line # returns union all glyph bounds ##
#Populate
#Example
SkPaint paint;
SkFontMetrics fm;
paint.getFontMetrics(&fm);
SkRect fb = paint.getFontBounds();
SkDebugf("metrics bounds = { %g, %g, %g, %g }\n", fm.fXMin, fm.fTop, fm.fXMax, fm.fBottom );
SkDebugf("font bounds = { %g, %g, %g, %g }\n", fb.fLeft, fb.fTop, fb.fRight, fm.fBottom );
#StdOut
metrics bounds = { -12.2461, -14.7891, 21.5215, 5.55469 }
font bounds = { -12.2461, -14.7891, 21.5215, 5.55469 }
##
##
##
#Subtopic Font_Metrics ##
# ------------------------------------------------------------------------------
#Method int textToGlyphs(const void* text, size_t byteLength,
SkGlyphID glyphs[]) const
#In Utility
#Line # converts text into glyph indices ##
#Populate
#Example
#Height 64
void draw(SkCanvas* canvas) {
SkPaint paint;
const uint8_t utf8[] = { 0x24, 0xC2, 0xA2, 0xE2, 0x82, 0xAC, 0xC2, 0xA5, 0xC2, 0xA3 };
std::vector<SkGlyphID> glyphs;
int count = paint.textToGlyphs(utf8, sizeof(utf8), nullptr);
glyphs.resize(count);
(void) paint.textToGlyphs(utf8, sizeof(utf8), &glyphs.front());
paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
paint.setTextSize(32);
canvas->drawText(&glyphs.front(), glyphs.size() * sizeof(SkGlyphID), 10, 40, paint);
}
##
##
#Method int countText(const void* text, size_t byteLength) const
#In Utility
#Line # returns number of Glyphs in text ##
#Populate
#Example
SkPaint paint;
const uint8_t utf8[] = { 0x24, 0xC2, 0xA2, 0xE2, 0x82, 0xAC, 0xC2, 0xA5, 0xC2, 0xA3 };
SkDebugf("count = %d\n", paint.countText(utf8, sizeof(utf8)));
#StdOut
count = 5
##
##
##
# ------------------------------------------------------------------------------
#Method bool containsText(const void* text, size_t byteLength) const
#In Utility
#Line # returns if all text corresponds to Glyphs ##
#Populate
#NoExample
#Description
containsText succeeds for degree symbol, but cannot find a glyph index
corresponding to the Unicode surrogate code point.
##
SkPaint paint;
const uint16_t goodChar = 0x00B0; // degree symbol
const uint16_t badChar = 0xD800; // Unicode surrogate
paint.setTextEncoding(SkPaint::kUTF16_TextEncoding);
SkDebugf("0x%04x %c= has char\n", goodChar,
paint.containsText(&goodChar, 2) ? '=' : '!');
SkDebugf("0x%04x %c= has char\n", badChar,
paint.containsText(&badChar, 2) ? '=' : '!');
#StdOut
0x00b0 == has char
0xd800 != has char
##
##
#Example
#Description
containsText returns true that glyph index is greater than zero, not
that it corresponds to an entry in Typeface.
##
SkPaint paint;
const uint16_t goodGlyph = 511;
const uint16_t zeroGlyph = 0;
const uint16_t badGlyph = 65535; // larger than glyph count in font
paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
SkDebugf("0x%04x %c= has glyph\n", goodGlyph,
paint.containsText(&goodGlyph, 2) ? '=' : '!');
SkDebugf("0x%04x %c= has glyph\n", zeroGlyph,
paint.containsText(&zeroGlyph, 2) ? '=' : '!');
SkDebugf("0x%04x %c= has glyph\n", badGlyph,
paint.containsText(&badGlyph, 2) ? '=' : '!');
#StdOut
0x01ff == has glyph
0x0000 != has glyph
0xffff == has glyph
##
##
#SeeAlso setTextEncoding Typeface
##
# ------------------------------------------------------------------------------
#Method void glyphsToUnichars(const SkGlyphID glyphs[],
int count, SkUnichar text[]) const
#In Utility
#Line # converts Glyphs into text ##
#Populate
#Example
#Height 64
#Description
Convert UTF-8 text to glyphs; then convert glyphs to Unichar code points.
##
void draw(SkCanvas* canvas) {
SkPaint paint;
const char hello[] = "Hello!";
const int count = sizeof(hello) - 1;
SkGlyphID glyphs[count];
if (count != paint.textToGlyphs(hello, count, glyphs)) {
return;
}
SkUnichar unichars[count];
paint.glyphsToUnichars(glyphs, count, unichars);
paint.setTextEncoding(SkPaint::kUTF32_TextEncoding);
canvas->drawText(unichars, sizeof(unichars), 10, 30, paint);
}
##
##
# ------------------------------------------------------------------------------
#Subtopic Measure_Text
#Line # width, height, bounds of text ##
#Method SkScalar measureText(const void* text, size_t length, SkRect* bounds) const
#In Measure_Text
#Line # returns advance width and bounds of text ##
#Populate
#Example
#Height 64
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(50);
const char str[] = "ay^jZ";
const int count = sizeof(str) - 1;
canvas->drawText(str, count, 25, 50, paint);
SkRect bounds;
paint.measureText(str, count, &bounds);
canvas->translate(25, 50);
paint.setStyle(SkPaint::kStroke_Style);
canvas->drawRect(bounds, paint);
}
##
##
#Method SkScalar measureText(const void* text, size_t length) const
#In Measure_Text
#Populate
#Example
SkPaint paint;
SkDebugf("default width = %g\n", paint.measureText("!", 1));
paint.setTextSize(paint.getTextSize() * 2);
SkDebugf("double width = %g\n", paint.measureText("!", 1));
#StdOut
default width = 5
double width = 10
##
##
##
#Method size_t breakText(const void* text, size_t length, SkScalar maxWidth,
SkScalar* measuredWidth = nullptr) const
#In Measure_Text
#Line # returns text that fits in a width ##
#Populate
#Example
#Description
Line under "Breakfast" shows desired width, shorter than available characters.
Line under "Bre" shows measured width after breaking text.
##
#Height 128
#Width 280
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(50);
const char str[] = "Breakfast";
const int count = sizeof(str) - 1;
canvas->drawText(str, count, 25, 50, paint);
SkScalar measuredWidth;
int partialBytes = paint.breakText(str, count, 100, &measuredWidth);
canvas->drawText(str, partialBytes, 25, 100, paint);
canvas->drawLine(25, 60, 25 + 100, 60, paint);
canvas->drawLine(25, 110, 25 + measuredWidth, 110, paint);
}
##
##
#Method int getTextWidths(const void* text, size_t byteLength, SkScalar widths[],
SkRect bounds[] = nullptr) const
#In Measure_Text
#Line # returns advance and bounds for each glyph in text ##
#Populate
#Example
#Height 160
#Description
Bounds of Glyphs increase for stroked text, but text advance remains the same.
The underlines show the text advance, spaced to keep them distinct.
##
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setAntiAlias(true);
paint.setTextSize(50);
const char str[] = "abc";
const int bytes = sizeof(str) - 1;
int count = paint.getTextWidths(str, bytes, nullptr);
std::vector<SkScalar> widths;
std::vector<SkRect> bounds;
widths.resize(count);
bounds.resize(count);
for (int loop = 0; loop < 2; ++loop) {
(void) paint.getTextWidths(str, count, &widths.front(), &bounds.front());
SkPoint loc = { 25, 50 };
canvas->drawText(str, bytes, loc.fX, loc.fY, paint);
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(0);
SkScalar advanceY = loc.fY + 10;
for (int index = 0; index < count; ++index) {
bounds[index].offset(loc.fX, loc.fY);
canvas->drawRect(bounds[index], paint);
canvas->drawLine(loc.fX, advanceY, loc.fX + widths[index], advanceY, paint);
loc.fX += widths[index];
advanceY += 5;
}
canvas->translate(0, 80);
paint.setStrokeWidth(3);
}
}
##
##
#Subtopic Measure_Text ##
# ------------------------------------------------------------------------------
#Subtopic Text_Path
#Line # geometry of Glyphs ##
Text_Path describes the geometry of Glyphs used to draw text.
#Method void getTextPath(const void* text, size_t length, SkScalar x, SkScalar y,
SkPath* path) const
#In Text_Path
#Line # returns Path equivalent to text ##
#Populate
#Example
#Description
Text is added to Path, offset, and subtracted from Path, then added at
the offset location. The result is rendered with one draw call.
##
#Height 128
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setTextSize(80);
SkPath path, path2;
paint.getTextPath("ABC", 3, 20, 80, &path);
path.offset(20, 20, &path2);
Op(path, path2, SkPathOp::kDifference_SkPathOp, &path);
path.addPath(path2);
paint.setStyle(SkPaint::kStroke_Style);
canvas->drawPath(path, paint);
}
##
##
#Method void getPosTextPath(const void* text, size_t length,
const SkPoint pos[], SkPath* path) const
#In Text_Path
#Line # returns Path equivalent to positioned text ##
#Populate
#Example
#Height 85
#Description
Simplifies three Glyphs to eliminate overlaps, and strokes the result.
##
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setTextSize(80);
SkPath path, path2;
SkPoint pos[] = {{20, 60}, {30, 70}, {40, 80}};
paint.getPosTextPath("ABC", 3, pos, &path);
Simplify(path, &path);
paint.setStyle(SkPaint::kStroke_Style);
canvas->drawPath(path, paint);
}
##
##
#Subtopic Text_Path ##
# ------------------------------------------------------------------------------
#Subtopic Text_Intercepts
#Line # advanced underline, strike through ##
Text_Intercepts describe the intersection of drawn text Glyphs with a pair
of lines parallel to the text advance. Text_Intercepts permits creating a
underline that skips Descenders.
#Method int getTextIntercepts(const void* text, size_t length, SkScalar x, SkScalar y,
const SkScalar bounds[2], SkScalar* intervals) const
#In Text_Intercepts
#Line # returns where lines intersect text; underlines ##
#Populate
#Example
#Height 128
#Description
Underline uses intercepts to draw on either side of the glyph Descender.
##
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setTextSize(120);
SkPoint textOrigin = { 20, 100 };
SkScalar bounds[] = { 100, 108 };
int count = paint.getTextIntercepts("y", 1, textOrigin.fX, textOrigin.fY, bounds, nullptr);
std::vector<SkScalar> intervals;
intervals.resize(count);
(void) paint.getTextIntercepts("y", 1, textOrigin.fX, textOrigin.fY, bounds,
&intervals.front());
canvas->drawString("y", textOrigin.fX, textOrigin.fY, paint);
paint.setColor(SK_ColorRED);
SkScalar x = textOrigin.fX;
for (int i = 0; i < count; i += 2) {
canvas->drawRect({x, bounds[0], intervals[i], bounds[1]}, paint);
x = intervals[i + 1];
}
canvas->drawRect({intervals[count - 1], bounds[0],
textOrigin.fX + paint.measureText("y", 1), bounds[1]}, paint);
}
##
##
#Method int getPosTextIntercepts(const void* text, size_t length, const SkPoint pos[],
const SkScalar bounds[2], SkScalar* intervals) const
#In Text_Intercepts
#Line # returns where lines intersect positioned text; underlines ##
#Populate
#Example
#Description
Text intercepts draw on either side of, but not inside, Glyphs in a run.
##
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setTextSize(120);
SkPoint textPos[] = {{ 60, 90 }, { 120, 90 }};
SkScalar bounds[] = { 40, 70 };
const char str[] = "A+";
int len = sizeof(str) - 1;
int count = paint.getPosTextIntercepts(str, len, textPos, bounds, nullptr);
std::vector<SkScalar> intervals;
intervals.resize(count);
(void) paint.getPosTextIntercepts(str, len, textPos, bounds, &intervals.front());
canvas->drawPosText(str, len, textPos, paint);
paint.setColor(SK_ColorRED);
SkScalar x = textPos[0].fX;
for (int i = 0; i < count; i+= 2) {
canvas->drawRect({x, bounds[0], intervals[i], bounds[1]}, paint);
x = intervals[i + 1];
}
if (count) {
canvas->drawRect({intervals[count - 1], bounds[0], 180, bounds[1]}, paint);
}
}
##
##
#Method int getPosTextHIntercepts(const void* text, size_t length, const SkScalar xpos[],
SkScalar constY, const SkScalar bounds[2],
SkScalar* intervals) const
#In Text_Intercepts
#Line # returns where lines intersect horizontally positioned text; underlines ##
#Populate
#Example
#Height 128
#Description
Text intercepts do not take stroke thickness into consideration.
##
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setTextSize(120);
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(4);
SkScalar textPosH[] = { 20, 80, 140 };
SkScalar y = 100;
SkScalar bounds[] = { 56, 78 };
const char str[] = "\\-/";
int len = sizeof(str) - 1;
int count = paint.getPosTextHIntercepts(str, len, textPosH, y, bounds, nullptr);
std::vector<SkScalar> intervals;
intervals.resize(count);
(void) paint.getPosTextHIntercepts(str, len, textPosH, y, bounds, &intervals.front());
canvas->drawPosTextH(str, len, textPosH, y, paint);
paint.setColor(0xFFFF7777);
paint.setStyle(SkPaint::kFill_Style);
SkScalar x = textPosH[0];
for (int i = 0; i < count; i+= 2) {
canvas->drawRect({x, bounds[0], intervals[i], bounds[1]}, paint);
x = intervals[i + 1];
}
canvas->drawRect({intervals[count - 1], bounds[0], 180, bounds[1]}, paint);
}
##
##
#Method int getTextBlobIntercepts(const SkTextBlob* blob, const SkScalar bounds[2],
SkScalar* intervals) const
#In Text_Intercepts
#Line # returns where lines intersect Text_Blob; underlines ##
#Populate
#Example
#Height 143
void draw(SkCanvas* canvas) {
SkPaint paint;
paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
paint.setTextSize(120);
SkPoint textPos = { 20, 110 };
int len = 3;
SkTextBlobBuilder textBlobBuilder;
const SkTextBlobBuilder::RunBuffer& run =
textBlobBuilder.allocRun(paint, len, textPos.fX, textPos.fY);
run.glyphs[0] = 10;
run.glyphs[1] = 20;
run.glyphs[2] = 30;
sk_sp<const SkTextBlob> blob = textBlobBuilder.make();
canvas->drawTextBlob(blob.get(), textPos.fX, textPos.fY, paint);
SkScalar bounds[] = { 116, 134 };
int count = paint.getTextBlobIntercepts(blob.get(), bounds, nullptr);
std::vector<SkScalar> intervals;
intervals.resize(count);
(void) paint.getTextBlobIntercepts(blob.get(), bounds, &intervals.front());
canvas->drawTextBlob(blob.get(), 0, 0, paint);
paint.setColor(0xFFFF7777);
SkScalar x = textPos.fX;
for (int i = 0; i < count; i+= 2) {
canvas->drawRect({x, bounds[0], intervals[i], bounds[1]}, paint);
x = intervals[i + 1];
}
canvas->drawRect({intervals[count - 1], bounds[0], 180, bounds[1]}, paint);
}
##
##
#Subtopic Text_Intercepts ##
# ------------------------------------------------------------------------------
#Method bool nothingToDraw() const
#In Utility
#Line # returns true if Paint prevents all drawing ##
#Populate
#Example
void draw(SkCanvas* canvas) {
auto debugster = [](const char* prefix, const SkPaint& p) -> void {
SkDebugf("%s nothing to draw: %s\n", prefix,
p.nothingToDraw() ? "true" : "false");
};
SkPaint paint;
debugster("initial", paint);
paint.setBlendMode(SkBlendMode::kDst);
debugster("blend dst", paint);
paint.setBlendMode(SkBlendMode::kSrcOver);
debugster("blend src over", paint);
paint.setAlpha(0);
debugster("alpha 0", paint);
}
#StdOut
initial nothing to draw: false
blend dst nothing to draw: true
blend src over nothing to draw: false
alpha 0 nothing to draw: true
#StdOut ##
##
##
# ------------------------------------------------------------------------------
#Subtopic Fast_Bounds
#Line # approximate area required by Paint ##
#Private
To be made private.
##
Fast_Bounds functions conservatively outset a drawing bounds by additional area
Paint may draw to.
#Method bool canComputeFastBounds() const
#In Fast_Bounds
#Line # returns true if settings allow for fast bounds computation ##
#Private
(to be made private)
##
Returns true if Paint does not include elements requiring extensive computation
to compute Device bounds of drawn geometry. For instance, Paint with Path_Effect
always returns false.
#Return true if Paint allows for fast computation of bounds ##
##
#Method const SkRect& computeFastBounds(const SkRect& orig, SkRect* storage) const
#In Fast_Bounds
#Line # returns fill bounds for quick reject tests ##
#Private
(to be made private)
##
Only call this if canComputeFastBounds returned true. This takes a
raw rectangle (the raw bounds of a shape), and adjusts it for stylistic
effects in the paint (e.g. stroking). If needed, it uses the storage
parameter. It returns the adjusted bounds that can then be used
for SkCanvas::quickReject tests.
The returned Rect will either be orig or storage, thus the caller
should not rely on storage being set to the result, but should always
use the returned value. It is legal for orig and storage to be the same
Rect.
#Private
For example:
if (!path.isInverseFillType() && paint.canComputeFastBounds()) {
SkRect storage;
if (canvas->quickReject(paint.computeFastBounds(path.getBounds(), &storage))) {
return; // do not draw the path
}
}
// draw the path
##
#Param orig geometry modified by Paint when drawn ##
#Param storage computed bounds of geometry; may not be nullptr ##
#Return fast computed bounds ##
##
#Method const SkRect& computeFastStrokeBounds(const SkRect& orig,
SkRect* storage) const
#In Fast_Bounds
#Line # returns stroke bounds for quick reject tests ##
#Private
(to be made private)
##
#Param orig geometry modified by Paint when drawn ##
#Param storage computed bounds of geometry ##
#Return fast computed bounds ##
##
#Method const SkRect& doComputeFastBounds(const SkRect& orig, SkRect* storage,
Style style) const
#In Fast_Bounds
#Line # returns bounds for quick reject tests ##
#Private
(to be made private)
##
Computes the bounds, overriding the Paint Style. This can be used to
account for additional width required by stroking orig, without
altering Style set to fill.
#Param orig geometry modified by Paint when drawn ##
#Param storage computed bounds of geometry ##
#Param style overrides Style ##
#Return fast computed bounds ##
##
#Subtopic Fast_Bounds ##
# ------------------------------------------------------------------------------
#Subtopic Utility
#Line # rarely called management functions ##
##
# ------------------------------------------------------------------------------
#Class SkPaint ##
#Topic Paint ##
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