skia2/site/user/api/SkImageInfo_Reference.md

SkImageInfo Reference

Image Info

Image Info specifies the dimensions and encoding of the pixels in a Bitmap. The dimensions are integral width and height. The encoding is how pixel bits describe Color Alpha, transparency; Color components red, blue, and green; and Color Space, the range and linearity of colors.

Image Info describes an uncompressed raster pixels. In contrast, Image additionally describes compressed pixels like PNG, and Surface describes destinations on the GPU. Image and Surface may be specified by Image Info, but Image and Surface may not contain Image Info.

Overview

Topic	Description
Constructors	functions that construct SkImageInfo
Functions	global and class member functions
Operators	operator overloading methods
Related Functions	similar member functions grouped together

Constant

SkImageInfo related constants are defined by enum, enum class, #define, const, and constexpr.

Topic	Description
SkAlphaType	encoding for pixel transparency
SkColorType	encoding for pixel color
SkYUVColorSpace	color range of YUV pixels
kARGB_4444_SkColorType	pixel with 4 bits for alpha, red, green, blue; in 16-bit word
kAlpha_8_SkColorType	pixel with Alpha in 8-bit byte
kBGRA_8888_SkColorType	pixel with 8 bits for blue, green, red, alpha; in 32-bit word
kGray_8_SkColorType	pixel with grayscale level in 8-bit byte
kJPEG_SkYUVColorSpace	describes full range
kLastEnum_SkAlphaType	last valid value
kLastEnum_SkColorType	last valid value
kLastEnum_SkYUVColorSpace	last valid value
kN32_SkColorType	native ARGB 32-bit encoding
kOpaque_SkAlphaType	pixel is opaque
kPremul_SkAlphaType	pixel components are Premultiplied by Alpha
kRGBA_1010102_SkColorType	10 bits for red, green, blue; 2 bits for alpha; in 32-bit word
kRGBA_8888_SkColorType	pixel with 8 bits for red, green, blue, alpha; in 32-bit word
kRGBA_F16_SkColorType	pixel with half floats for red, green, blue, alpha; in 64-bit word
kRGB_101010x_SkColorType	pixel with 10 bits each for red, green, blue; in 32-bit word
kRGB_565_SkColorType	pixel with 5 bits red, 6 bits green, 5 bits blue, in 16-bit word
kRGB_888x_SkColorType	pixel with 8 bits each for red, green, blue; in 32-bit word
kRec601_SkYUVColorSpace	describes SDTV range
kRec709_SkYUVColorSpace	describes HDTV range
kUnknown_SkAlphaType	uninitialized
kUnknown_SkColorType	uninitialized
kUnpremul_SkAlphaType	pixel components are independent of Alpha

Alpha Type

Enum SkAlphaType

    enum SkAlphaType {
        kUnknown_SkAlphaType,
        kOpaque_SkAlphaType,
        kPremul_SkAlphaType,
        kUnpremul_SkAlphaType,
        kLastEnum_SkAlphaType = kUnpremul_SkAlphaType,
    };

Describes how to interpret the alpha component of a pixel. A pixel may be opaque, or Color Alpha, describing multiple levels of transparency.

In simple blending, Color Alpha weights the draw color and the destination color to create a new color. If alpha describes a weight from zero to one:

    new color = draw color * alpha + destination color * (1 - alpha)

In practice alpha is encoded in two or more bits, where 1.0 equals all bits set.

RGB may have Color Alpha included in each component value; the stored value is the original RGB multiplied by Color Alpha. Premultiplied color components improve performance.

Constants

Const	Value	Details	Description
kUnknown_SkAlphaType	0		Alpha Type is uninitialized.
kOpaque_SkAlphaType	1	Alpha Type Opaque	Pixels are opaque. The Color Type must have no explicit alpha component, or all alpha components must be set to their maximum value.
kPremul_SkAlphaType	2	Alpha Type Premul	Pixels have Alpha Premultiplied into color components. Surface pixels must be Premultiplied.
kUnpremul_SkAlphaType	3	Alpha Type Unpremul	Pixel color component values are independent of alpha value. Images generated from encoded data like PNG do not Premultiply pixel color components. kUnpremul_SkAlphaType is supported for Image pixels, but not for Surface pixels.
kLastEnum_SkAlphaType	3		Used by tests to iterate through all valid values.

See Also

SkColorType SkColorSpace

Alpha Type Opaque

Use kOpaque_SkAlphaType as a hint to optimize drawing when Alpha component of all pixel is set to its maximum value of 1.0; all alpha component bits are set. If Image Info is set to kOpaque_SkAlphaType but all alpha values are not 1.0, results are undefined.

Example

SkPreMultiplyARGB parameter a is set to 255, its maximum value, and is interpreted as Color Alpha of 1.0. kOpaque_SkAlphaType may be set to improve performance. If SkPreMultiplyARGB parameter a is set to a value smaller than 255, kPremul_SkAlphaType must be used instead to avoid undefined results. The four displayed values are the original component values, though not necessarily in the same order.

Alpha Type Premul

Use kPremul_SkAlphaType when stored color components are the original color multiplied by the alpha component. The alpha component range of 0.0 to 1.0 is achieved by dividing the integer bit value by the maximum bit value.

stored color = original color * alpha / max alpha

The color component must be equal to or smaller than the alpha component, or the results are undefined.

Example

SkPreMultiplyARGB parameter a is set to 150, less than its maximum value, and is interpreted as Color Alpha of about 0.6. kPremul_SkAlphaType must be set, since SkPreMultiplyARGB parameter a is set to a value smaller than 255, to avoid undefined results. The four displayed values reflect that the alpha component has been multiplied by the original color.

Alpha Type Unpremul

Use kUnpremul_SkAlphaType if stored color components are not divided by the alpha component. Some drawing destinations may not support kUnpremul_SkAlphaType.

Example

SkColorSetARGB parameter a is set to 150, less than its maximum value, and is interpreted as Color Alpha of about 0.6. color is not Premultiplied; color components may have values greater than color alpha. The four displayed values are the original component values, though not necessarily in the same order.

SkAlphaTypeIsOpaque

static inline bool SkAlphaTypeIsOpaque(SkAlphaType at)

Returns true if Alpha Type equals kOpaque_SkAlphaType. kOpaque_SkAlphaType is a hint that the Color Type is opaque, or that all Color Alpha values are set to their 1.0 equivalent. If Alpha Type is kOpaque_SkAlphaType, and Color Type is not opaque, then the result of drawing any pixel with a Color Alpha value less than 1.0 is undefined.

Parameters

at	one of: kUnknown_SkAlphaType, kOpaque_SkAlphaType, kPremul_SkAlphaType, kUnpremul_SkAlphaType

Return Value

true if at equals kOpaque_SkAlphaType

---

Color Type

Enum SkColorType

    enum SkColorType {
        kUnknown_SkColorType,
        kAlpha_8_SkColorType,
        kRGB_565_SkColorType,
        kARGB_4444_SkColorType,
        kRGBA_8888_SkColorType,
        kRGB_888x_SkColorType,
        kBGRA_8888_SkColorType,
        kRGBA_1010102_SkColorType,
        kRGB_101010x_SkColorType,
        kGray_8_SkColorType,
        kRGBA_F16_SkColorType,

        kLastEnum_SkColorType = kRGBA_F16_SkColorType,
    #if SK_PMCOLOR_BYTE_ORDER(B,G,R,A)
        kN32_SkColorType = kBGRA_8888_SkColorType,
    #elif SK_PMCOLOR_BYTE_ORDER(R,G,B,A)
        kN32_SkColorType = kRGBA_8888_SkColorType,
    #else
        #error
    #endif
    };

Describes how pixel bits encode color. A pixel may be an alpha mask, a grayscale, RGB, or ARGB.

kN32_SkColorType selects the native 32-bit ARGB format. On Little_Endian processors, pixels containing 8-bit ARGB components pack into 32-bit kBGRA_8888_SkColorType. On Big_Endian processors, pixels pack into 32-bit kRGBA_8888_SkColorType.

Constants

Const	Value	Details	Description
kUnknown_SkColorType	0		Color Type is set to kUnknown_SkColorType by default. If set, encoding format and size is unknown.
kAlpha_8_SkColorType	1	Color Type Alpha 8	Stores 8-bit byte pixel encoding that represents transparency. Value of zero is completely transparent; a value of 255 is completely opaque.
kRGB_565_SkColorType	2	Color Type RGB 565	Stores 16-bit word pixel encoding that contains five bits of blue, six bits of green, and five bits of red.
kARGB_4444_SkColorType	3	Color Type ARGB 4444	Stores 16-bit word pixel encoding that contains four bits of alpha, four bits of blue, four bits of green, and four bits of red.
kRGBA_8888_SkColorType	4	Color Type RGBA 8888	Stores 32-bit word pixel encoding that contains eight bits of red, eight bits of green, eight bits of blue, and eight bits of alpha.
kRGB_888x_SkColorType	5	Color Type RGB 888	Stores 32-bit word pixel encoding that contains eight bits of red, eight bits of green, eight bits of blue, and eight unused bits.
kBGRA_8888_SkColorType	6	Color Type BGRA 8888	Stores 32-bit word pixel encoding that contains eight bits of blue, eight bits of green, eight bits of red, and eight bits of alpha.
kRGBA_1010102_SkColorType	7	Color Type RGBA 1010102	Stores 32-bit word pixel encoding that contains ten bits of red, ten bits of green, ten bits of blue, and two bits of alpha.
kRGB_101010x_SkColorType	8	Color Type RGB 101010	Stores 32-bit word pixel encoding that contains ten bits of red, ten bits of green, ten bits of blue, and two unused bits.
kGray_8_SkColorType	9	Color Type Gray 8	Stores 8-bit byte pixel encoding that equivalent to equal values for red, blue, and green, representing colors from black to white.
kRGBA_F16_SkColorType	10	Color Type RGBA F16	Stores 64-bit word pixel encoding that contains 16 bits of blue, 16 bits of green, 16 bits of red, and 16 bits of alpha.
kLastEnum_SkColorType	10		Used by tests to iterate through all valid values.
kN32_SkColorType	4 or 6		Encodes ARGB as either kRGBA_8888_SkColorType or kBGRA_8888_SkColorType, whichever is native to the platform.

See Also

SkAlphaType SkColorSpace

Color Type Alpha 8

Alpha pixels encode transparency without color information. Value of zero is completely transparent; a value of 255 is completely opaque. Bitmap pixels do not visibly draw, because its pixels have no color information. When SkColorType is set to kAlpha_8_SkColorType, the paired SkAlphaType is ignored.

Example

Alpha pixels can modify another draw. orangePaint fills the bounds of bitmap, with its transparency set to alpha8 pixel value.

See Also

Alpha Gray 8

Color Type RGB 565

kRGB_565_SkColorType encodes RGB to fit in a 16-bit word. Red and blue components use five bits describing 32 levels. Green components, more sensitive to the eye, use six bits describing 64 levels. kRGB_565_SkColorType has no bits for Alpha. Pixels are fully opaque as if its Color Alpha was set to one, and should always be paired with kOpaque_SkAlphaType.

Example

See Also

ARGB 4444 RGBA 8888

Color Type ARGB 4444

kARGB_4444_SkColorType encodes ARGB to fit in 16-bit word. Each component: alpha, blue, green, and red; use four bits, describing 16 levels. Note that kARGB_4444_SkColorType is misnamed; the acronym does not describe the actual component order.

If paired with kPremul_SkAlphaType: blue, green, and red components are Premultiplied by the alpha value. If blue, green, or red is greater than alpha, the drawn result is undefined.

If paired with kUnpremul_SkAlphaType: alpha, blue, green, and red components may have any value. There may be a performance penalty with Unpremultipled pixels.

If paired with kOpaque_SkAlphaType: all alpha component values are at the maximum; blue, green, and red components are fully opaque. If any alpha component is less than 15, the drawn result is undefined.

Example

See Also

RGBA 8888

Color Type RGBA 8888

kRGBA_8888_SkColorType encodes ARGB into a 32-bit word. Each component: red, green, blue, alpha; use eight bits, describing 256 levels.

If paired with kPremul_SkAlphaType: red, green, and blue components are Premultiplied by the alpha value. If red, green, or blue is greater than alpha, the drawn result is undefined.

If paired with kUnpremul_SkAlphaType: alpha, red, green, and blue components may have any value. There may be a performance penalty with Unpremultipled pixels.

If paired with kOpaque_SkAlphaType: all alpha component values are at the maximum; red, green, and blue components are fully opaque. If any alpha component is less than 255, the drawn result is undefined.

On Big_Endian platforms, kRGBA_8888_SkColorType is the native Color Type, and will have the best performance. Use kN32_SkColorType to choose the best Color Type for the platform at compile time.

Example

See Also

RGB 888 BGRA 8888

Color Type RGB 888

kRGB_888x_SkColorType encodes RGB into a 32-bit word. Each component: red, green, blue; use eight bits, describing 256 levels. Eight bits are unused. Pixels described by kRGB_888x_SkColorType are fully opaque as if their Color Alpha was set to one, and should always be paired with kOpaque_SkAlphaType.

Example

See Also

RGBA 8888 BGRA 8888

Color Type BGRA 8888

kBGRA_8888_SkColorType encodes ARGB into a 32-bit word. Each component: blue, green, red, and alpha; use eight bits, describing 256 levels.

If paired with kPremul_SkAlphaType: blue, green, and red components are Premultiplied by the alpha value. If blue, green, or red is greater than alpha, the drawn result is undefined.

If paired with kUnpremul_SkAlphaType: blue, green, red, and alpha components may have any value. There may be a performance penalty with Unpremultiplied pixels.

If paired with kOpaque_SkAlphaType: all alpha component values are at the maximum; blue, green, and red components are fully opaque. If any alpha component is less than 255, the drawn result is undefined.

On Little_Endian platforms, kBGRA_8888_SkColorType is the native Color Type, and will have the best performance. Use kN32_SkColorType to choose the best Color Type for the platform at compile time.

Example

See Also

RGBA 8888

Color Type RGBA 1010102

kRGBA_1010102_SkColorType encodes ARGB into a 32-bit word. Each Color component: red, green, and blue; use ten bits, describing 1024 levels. Two bits contain alpha, describing four levels. Possible alpha values are zero: fully transparent; one: 33% opaque; two: 67% opaque; three: fully opaque.

At present, Color in Paint does not provide enough precision to draw all colors possible to a kRGBA_1010102_SkColorType Surface.

If paired with kPremul_SkAlphaType: red, green, and blue components are Premultiplied by the alpha value. If red, green, or blue is greater than the alpha replicated to ten bits, the drawn result is undefined.

If paired with kUnpremul_SkAlphaType: alpha, red, green, and blue components may have any value. There may be a performance penalty with Unpremultiplied pixels.

If paired with kOpaque_SkAlphaType: all alpha component values are at the maximum; red, green, and blue components are fully opaque. If any alpha component is less than three, the drawn result is undefined.

Example

See Also

RGB 101010 RGBA 8888

Color Type RGB 101010

kRGB_101010x_SkColorType encodes RGB into a 32-bit word. Each Color component: red, green, and blue; use ten bits, describing 1024 levels. Two bits are unused. Pixels described by kRGB_101010x_SkColorType are fully opaque as if its Color Alpha was set to one, and should always be paired with kOpaque_SkAlphaType.

At present, Color in Paint does not provide enough precision to draw all colors possible to a kRGB_101010x_SkColorType Surface.

Example

See Also

RGBA 1010102

Color Type Gray 8

kGray_8_SkColorType encodes grayscale level in eight bits that is equivalent to equal values for red, blue, and green, representing colors from black to white. Pixels described by kGray_8_SkColorType are fully opaque as if its Color Alpha was set to one, and should always be paired with kOpaque_SkAlphaType.

Example

See Also

Alpha 8

Color Type RGBA F16

kRGBA_F16_SkColorType encodes ARGB into a 64-bit word. Each component: blue, green, red, and alpha; use 16 bits, describing a floating point value. from -65500 to 65000 with 3.31 decimal digits of precision.

At present, Color in Paint does not provide enough precision or range to draw all colors possible to a kRGBA_F16_SkColorType Surface.

Each component encodes a floating point value using Half floats . Meaningful colors are represented by the range 0.0 to 1.0, although smaller and larger values may be useful when used in combination with Transfer Mode.

If paired with kPremul_SkAlphaType: blue, green, and red components are Premultiplied by the alpha value. If blue, green, or red is greater than alpha, the drawn result is undefined.

If paired with kUnpremul_SkAlphaType: blue, green, red, and alpha components may have any value. There may be a performance penalty with Unpremultiplied pixels.

If paired with kOpaque_SkAlphaType: all alpha component values are at the maximum; blue, green, and red components are fully opaque. If any alpha component is less than 255, the drawn result is undefined.

Example

See Also

SkColor4f

SkColorTypeBytesPerPixel

int SkColorTypeBytesPerPixel(SkColorType ct)

Returns the number of bytes required to store a pixel, including unused padding. Returns zero if ct is kUnknown_SkColorType or invalid.

Parameters

ct	one of: kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType

Return Value

bytes per pixel

Example

kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType

See Also

SkImageInfo::bytesPerPixel

---

SkColorTypeIsAlwaysOpaque

bool SkColorTypeIsAlwaysOpaque(SkColorType ct)

Returns true if Color Type always decodes Color Alpha to 1.0, making the pixel fully opaque. If true, Color Type does not reserve bits to encode Color Alpha.

Parameters

ct	one of: kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType

Return Value

true if Color Alpha is always set to 1.0

Example

kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType

See Also

SkColorTypeValidateAlphaType

---

SkColorTypeValidateAlphaType

bool SkColorTypeValidateAlphaType(SkColorType colorType, SkAlphaType alphaType,
                                  SkAlphaType* canonical = nullptr)

Returns true if canonical can be set to a valid Alpha Type for colorType. If there is more than one valid canonical Alpha Type, set to alphaType, if valid. If true is returned and canonical is not nullptr, store valid Alpha Type.

Returns false only if alphaType is kUnknown_SkAlphaType, color type is not kUnknown_SkColorType, and Color Type is not always opaque. If false is returned, canonical is ignored.

For kUnknown_SkColorType: set canonical to kUnknown_SkAlphaType and return true. For kAlpha_8_SkColorType: set canonical to kPremul_SkAlphaType or kOpaque_SkAlphaType and return true if alphaType is not kUnknown_SkAlphaType. For kRGB_565_SkColorType, kRGB_888x_SkColorType, kRGB_101010x_SkColorType, and kGray_8_SkColorType: set canonical to kOpaque_SkAlphaType and return true. For kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, and kRGBA_F16_SkColorType: set canonical to alphaType and return true if alphaType is not kUnknown_SkAlphaType.

Parameters

colorType	one of: kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType
alphaType	one of: kUnknown_SkAlphaType, kOpaque_SkAlphaType, kPremul_SkAlphaType, kUnpremul_SkAlphaType
canonical	storage for Alpha Type

Return Value

true if valid Alpha Type can be associated with colorType

Example

kUnknown_SkAlphaType, kOpaque_SkAlphaType, kPremul_SkAlphaType, kUnpremul_SkAlphaType kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType

See Also

SkColorTypeIsAlwaysOpaque

---

YUV ColorSpace

Enum SkYUVColorSpace

    enum SkYUVColorSpace {
        kJPEG_SkYUVColorSpace,
        kRec601_SkYUVColorSpace,
        kRec709_SkYUVColorSpace,
        kLastEnum_SkYUVColorSpace = kRec709_SkYUVColorSpace,
    };

Describes color range of YUV pixels. The color mapping from YUV to RGB varies depending on the source. YUV pixels may be generated by JPEG images, standard video streams, or high definition video streams. Each has its own mapping from YUV and RGB.

JPEG YUV values encode the full range of 0 to 255 for all three components. Video YUV values range from 16 to 235 for all three components. Details of encoding and conversion to RGB are described in YCbCr color space .

Constants

Const	Value	Description
kJPEG_SkYUVColorSpace	0	Describes standard JPEG color space; CCIR 601 with full range of 0 to 255 for components.
kRec601_SkYUVColorSpace	1	Describes standard used by standard definition television; CCIR 601 with studio range of 16 to 235 range for components.
kRec709_SkYUVColorSpace	2	Describes standard used by high definition television; Rec. 709 with studio range of 16 to 235 range for components.
kLastEnum_SkYUVColorSpace	2	Used by tests to iterate through all valid values.

See Also

SkImage::MakeFromYUVTexturesCopy SkImage::MakeFromNV12TexturesCopy

Struct SkImageInfo

Constant

SkImageInfo related constants are defined by enum, enum class, #define, const, and constexpr.

Topic	Description

Describes pixel dimensions and encoding. Bitmap, Image, PixMap, and Surface can be created from Image Info. Image Info can be retrieved from Bitmap and Pixmap, but not from Image and Surface. For example, Image and Surface implementations may defer pixel depth, so may not completely specify Image Info.

Image Info contains dimensions, the pixel integral width and height. It encodes how pixel bits describe Color Alpha, transparency; Color components red, blue, and green; and Color Space, the range and linearity of colors.

Member Function

SkImageInfo member functions read and modify the structure properties.

Topic	Description
ByteSizeOverflowed	checks result of computeByteSize and computeMinByteSize
Make	creates Image Info from dimensions, Color Type, Alpha Type, Color Space
MakeA8	creates Image Info with kAlpha_8_SkColorType, kPremul_SkAlphaType
MakeN32	creates Image Info with Native_Color_Type
MakeN32Premul	creates Image Info with Native_Color_Type, kPremul_SkAlphaType
MakeS32	creates Image Info with Native_Color_Type, sRGB Color Space
MakeUnknown	creates Image Info with kUnknown_SkColorType, kUnknown_SkAlphaType
SkAlphaTypeIsOpaque	returns if Alpha Type equals kOpaque_SkAlphaType
SkColorTypeBytesPerPixel	returns Color Type byte size
SkColorTypeIsAlwaysOpaque	returns if Color Type includes Color Alpha
SkColorTypeValidateAlphaType	returns if Alpha Type is valid
alphaType	returns Alpha Type
bounds	returns width and height as Rectangle
bytesPerPixel	returns number of bytes in pixel based on Color Type
colorSpace	returns Color Space
colorType	returns Color Type
computeByteSize	returns memory required by pixel buffer with given row bytes
computeMinByteSize	returns least memory required by pixel buffer
computeOffset	returns byte offset within pixel array
dimensions	returns width and height
gammaCloseToSRGB	returns if Color Space gamma is approximately the same as sRGB
height	returns pixel row count
isEmpty	returns if dimensions contain pixels
isOpaque	returns if Alpha Type is kOpaque_SkAlphaType
makeAlphaType	creates Image Info with changed Alpha Type
makeColorSpace	creates Image Info with changed Color Space
makeColorType	creates Image Info with changed Color Type
makeWH	creates Image Info with changed dimensions
minRowBytes	returns width times bytesPerPixel in 32 bits
minRowBytes64	returns width times bytesPerPixel in 64 bits
refColorSpace	returns Color Space
reset	sets zero dimensions, kUnknown_SkColorType, kUnknown_SkAlphaType
shiftPerPixel	returns bit shift from pixels to bytes
validRowBytes	checks if row bytes is large enough to contain pixel row
validate	asserts if Image Info is invalid (debug only)
width	returns pixel column count

Related Function

SkImageInfo global, struct, and class related member functions share a topic.

Topic	Description
Alpha Type	encoding for pixel transparency
Alpha Type Opaque	hints all pixels are opaque
Alpha Type Premul	stores components scaled by Alpha
Alpha Type Unpremul	stores components without Alpha scaling
Color Type	encoding for pixel color
Color Type ARGB 4444	encodes ARGB in 16 bits
Color Type Alpha 8	encodes transparency only
Color Type BGRA 8888	encodes ARGB Little_Endian in 32 bits
Color Type Gray 8	encodes level of grayscale in 8 bits
Color Type RGBA 1010102	encodes ARGB ten bits per color component
Color Type RGBA 8888	encodes ARGB Big_Endian in 32 bits
Color Type RGBA F16	encodes ARGB as half floats
Color Type RGB 101010	encodes RGB ten bits per color component
Color Type RGB 565	encodes RGB in 16 bits
Color Type RGB 888	encodes RGB in 32 bits
Property	metrics and attributes
Utility	rarely called management functions
YUV ColorSpace	color range of YUV pixels

Constructor

SkImageInfo can be constructed or initialized by these functions, including C++ class constructors.

Topic	Description
Make	creates Image Info from dimensions, Color Type, Alpha Type, Color Space
MakeA8	creates Image Info with kAlpha_8_SkColorType, kPremul_SkAlphaType
MakeN32	creates Image Info with Native_Color_Type
MakeN32Premul	creates Image Info with Native_Color_Type, kPremul_SkAlphaType
	MakeN32Premul(int width, int height, sk sp<SkColorSpace> cs = nullptr)
	MakeN32Premul(const SkISize& size)
MakeS32	creates Image Info with Native_Color_Type, sRGB Color Space
MakeUnknown	creates Image Info with kUnknown_SkColorType, kUnknown_SkAlphaType
	MakeUnknown(int width, int height)
	MakeUnknown()
SkImageInfo()	creates with zero dimensions, kUnknown_SkColorType, kUnknown_SkAlphaType
makeAlphaType	creates Image Info with changed Alpha Type
makeColorSpace	creates Image Info with changed Color Space
makeColorType	creates Image Info with changed Color Type
makeWH	creates Image Info with changed dimensions
reset	sets zero dimensions, kUnknown_SkColorType, kUnknown_SkAlphaType

SkImageInfo

SkImageInfo()

Creates an empty Image Info with kUnknown_SkColorType, kUnknown_SkAlphaType, a width and height of zero, and no Color Space.

Return Value

empty Image Info

Example

An empty Image Info may be passed to SkCanvas::accessTopLayerPixels as storage for the Canvas actual Image Info.

See Also

Make MakeN32 MakeS32 MakeA8

---

Make

static SkImageInfo Make(int width, int height, SkColorType ct, SkAlphaType at,
                        sk sp<SkColorSpace> cs = nullptr)

Creates Image Info from integral dimensions width and height, Color Type ct, Alpha Type at, and optionally Color Space cs.

If Color Space cs is nullptr and Image Info is part of drawing source: Color Space defaults to sRGB, mapping into Surface Color Space.

Parameters are not validated to see if their values are legal, or that the combination is supported.

Parameters

width	pixel column count; must be zero or greater
height	pixel row count; must be zero or greater
ct	one of: kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType
at	one of: kUnknown_SkAlphaType, kOpaque_SkAlphaType, kPremul_SkAlphaType, kUnpremul_SkAlphaType
cs	range of colors; may be nullptr

Return Value

created Image Info

Example

See Also

MakeN32 MakeN32Premul^[2] MakeS32 MakeA8

---

MakeN32

static SkImageInfo MakeN32(int width, int height, SkAlphaType at, sk sp<SkColorSpace> cs = nullptr)

Creates Image Info from integral dimensions width and height, kN32_SkColorType, Alpha Type at, and optionally Color Space cs. kN32_SkColorType will equal either kBGRA_8888_SkColorType or kRGBA_8888_SkColorType, whichever is optimal.

If Color Space cs is nullptr and Image Info is part of drawing source: Color Space defaults to sRGB, mapping into Surface Color Space.

Parameters are not validated to see if their values are legal, or that the combination is supported.

Parameters

width	pixel column count; must be zero or greater
height	pixel row count; must be zero or greater
at	one of: kUnknown_SkAlphaType, kOpaque_SkAlphaType, kPremul_SkAlphaType, kUnpremul_SkAlphaType
cs	range of colors; may be nullptr

Return Value

created Image Info

Example

See Also

Make MakeN32Premul^[2] MakeS32 MakeA8

---

MakeS32

static SkImageInfo MakeS32(int width, int height, SkAlphaType at)

Creates Image Info from integral dimensions width and height, kN32_SkColorType, Alpha Type at, with sRGB Color Space.

Parameters are not validated to see if their values are legal, or that the combination is supported.

Parameters

width	pixel column count; must be zero or greater
height	pixel row count; must be zero or greater
at	one of: kUnknown_SkAlphaType, kOpaque_SkAlphaType, kPremul_SkAlphaType, kUnpremul_SkAlphaType

Return Value

created Image Info

Example

Top gradient is drawn to offScreen without Color Space. It is darker than middle gradient, drawn to offScreen with sRGB Color Space. Bottom gradient shares bits with middle, but does not specify the Color Space in noColorSpaceBitmap. A source without Color Space is treated as sRGB; the bottom gradient is identical to the middle gradient.

See Also

Make MakeN32 MakeN32Premul^[2] MakeA8

---

MakeN32Premul

static SkImageInfo MakeN32Premul(int width, int height, sk sp<SkColorSpace> cs = nullptr)

Creates Image Info from integral dimensions width and height, kN32_SkColorType, kPremul_SkAlphaType, with optional Color Space.

If Color Space cs is nullptr and Image Info is part of drawing source: Color Space defaults to sRGB, mapping into Surface Color Space.

Parameters are not validated to see if their values are legal, or that the combination is supported.

Parameters

width	pixel column count; must be zero or greater
height	pixel row count; must be zero or greater
cs	range of colors; may be nullptr

Return Value

created Image Info

Example

See Also

MakeN32 MakeS32 MakeA8 Make

---

static SkImageInfo MakeN32Premul(const SkISize& size)

Creates Image Info from integral dimensions width and height, kN32_SkColorType, kPremul_SkAlphaType, with Color Space set to nullptr.

If Image Info is part of drawing source: Color Space defaults to sRGB, mapping into Surface Color Space.

Parameters are not validated to see if their values are legal, or that the combination is supported.

Parameters

size	width and height, each must be zero or greater

Return Value

created Image Info

Example

See Also

MakeN32 MakeS32 MakeA8 Make

---

MakeA8

static SkImageInfo MakeA8(int width, int height)

Creates Image Info from integral dimensions width and height, kAlpha_8_SkColorType, kPremul_SkAlphaType, with Color Space set to nullptr.

Parameters

width	pixel column count; must be zero or greater
height	pixel row count; must be zero or greater

Return Value

created Image Info

Example

See Also

MakeN32 MakeS32 Make

---

MakeUnknown

static SkImageInfo MakeUnknown(int width, int height)

Creates Image Info from integral dimensions width and height, kUnknown_SkColorType, kUnknown_SkAlphaType, with Color Space set to nullptr.

Returned Image Info as part of source does not draw, and as part of destination can not be drawn to.

Parameters

width	pixel column count; must be zero or greater
height	pixel row count; must be zero or greater

Return Value

created Image Info

Example

See Also

SkImageInfo() MakeN32 MakeS32 Make

---

static SkImageInfo MakeUnknown()

Creates Image Info from integral dimensions width and height set to zero, kUnknown_SkColorType, kUnknown_SkAlphaType, with Color Space set to nullptr.

Returned Image Info as part of source does not draw, and as part of destination can not be drawn to.

Return Value

created Image Info

Example

See Also

SkImageInfo() MakeN32 MakeS32 Make

---

Property

Topic	Description
SkAlphaTypeIsOpaque	returns if Alpha Type equals kOpaque_SkAlphaType
SkColorTypeBytesPerPixel	returns Color Type byte size
SkColorTypeIsAlwaysOpaque	returns if Color Type includes Color Alpha
SkColorTypeValidateAlphaType	returns if Alpha Type is valid
alphaType	returns Alpha Type
bounds	returns width and height as Rectangle
bytesPerPixel	returns number of bytes in pixel based on Color Type
colorSpace	returns Color Space
colorType	returns Color Type
dimensions	returns width and height
gammaCloseToSRGB	returns if Color Space gamma is approximately the same as sRGB
height	returns pixel row count
isEmpty	returns if dimensions contain pixels
isOpaque	returns if Alpha Type is kOpaque_SkAlphaType
minRowBytes	returns width times bytesPerPixel in 32 bits
minRowBytes64	returns width times bytesPerPixel in 64 bits
refColorSpace	returns Color Space
shiftPerPixel	returns bit shift from pixels to bytes
width	returns pixel column count

width

int width() const

Returns pixel count in each row.

Return Value

pixel width

Example

See Also

height SkBitmap::width SkPixelRef::width SkImage::width SkSurface::width

---

height

int height() const

Returns pixel row count.

Return Value

pixel height

Example

See Also

width SkBitmap::height SkPixelRef::height SkImage::height SkSurface::height

---

colorType

SkColorType colorType() const

Returns Color Type, one of: kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType.

Return Value

Color Type

Example

Example Output

color type: kAlpha_8_SkColorType

See Also

alphaType SkPixmap::colorType SkBitmap::colorType

---

alphaType

SkAlphaType alphaType() const

Returns Alpha Type, one of: kUnknown_SkAlphaType, kOpaque_SkAlphaType, kPremul_SkAlphaType, kUnpremul_SkAlphaType.

Return Value

Alpha Type

Example

Example Output

alpha type: kPremul_SkAlphaType

See Also

colorType SkPixmap::alphaType SkBitmap::alphaType

---

colorSpace

SkColorSpace* colorSpace() const

Returns Color Space, the range of colors. The reference count of Color Space is unchanged. The returned Color Space is immutable.

Return Value

Color Space, or nullptr

Example

SkColorSpace::MakeSRGBLinear creates Color Space with linear gamma and an sRGB gamut. This Color Space gamma is not close to sRGB gamma.

Example Output

gammaCloseToSRGB: false  gammaIsLinear: true  isSRGB: false

See Also

Color Space SkPixmap::colorSpace SkBitmap::colorSpace

---

refColorSpace

sk sp<SkColorSpace> refColorSpace() const

Returns smart pointer to Color Space, the range of colors. The smart pointer tracks the number of objects sharing this Color Space reference so the memory is released when the owners destruct.

The returned Color Space is immutable.

Return Value

Color Space wrapped in a smart pointer

Example

See Also

Color Space SkBitmap::refColorSpace

---

isEmpty

bool isEmpty() const

Returns if Image Info describes an empty area of pixels by checking if either width or height is zero or smaller.

Return Value

true if either dimension is zero or smaller

Example

Example Output

width: 0 height: 0 empty: true
width: 0 height: 2 empty: true
width: 2 height: 0 empty: true
width: 2 height: 2 empty: false

See Also

dimensions bounds SkBitmap::empty SkPixmap::bounds

---

isOpaque

bool isOpaque() const

Returns true if Alpha Type is set to hint that all pixels are opaque; their Color Alpha value is implicitly or explicitly 1.0. If true, and all pixels are not opaque, Skia may draw incorrectly.

Does not check if Color Type allows Alpha, or if any pixel value has transparency.

Return Value

true if Alpha Type is kOpaque_SkAlphaType

Example

Example Output

isOpaque: false
isOpaque: false
isOpaque: true
isOpaque: true

See Also

Color Alpha SkColorTypeValidateAlphaType SkBitmap::isOpaque SkImage::isOpaque SkPixmap::isOpaque

---

dimensions

SkISize dimensions() const

Returns ISize { width, height }.

Return Value

integral size of width and height

Example

Example Output

dimensionsAsBounds == bounds

See Also

width height bounds SkBitmap::dimensions

---

bounds

SkIRect bounds() const

Returns IRect { 0, 0, width, height }.

Return Value

integral rectangle from origin to width and height

Example

See Also

width height dimensions

---

gammaCloseToSRGB

bool gammaCloseToSRGB() const

Returns true if associated Color Space is not nullptr, and Color Space gamma is approximately the same as sRGB. This includes the sRGB transfer function as well as a gamma curve described by a 2.2 exponent.

Return Value

true if Color Space gamma is approximately the same as sRGB

Example

See Also

SkColorSpace::gammaCloseToSRGB

---

makeWH

SkImageInfo makeWH(int newWidth, int newHeight) const

Creates Image Info with the same Color Type, Color Space, and Alpha Type, with dimensions set to width and height.

Parameters

newWidth	pixel column count; must be zero or greater
newHeight	pixel row count; must be zero or greater

Return Value

created Image Info

Example

See Also

Make makeAlphaType makeColorSpace makeColorType

---

makeAlphaType

SkImageInfo makeAlphaType(SkAlphaType newAlphaType) const

Creates Image Info with same Color Type, Color Space, width, and height, with Alpha Type set to newAlphaType.

Created Image Info contains newAlphaType even if it is incompatible with Color Type, in which case Alpha Type in Image Info is ignored.

Parameters

newAlphaType

one of: kUnknown_SkAlphaType, kOpaque_SkAlphaType, kPremul_SkAlphaType, kUnpremul_SkAlphaType

Return Value

created Image Info

Example

See Also

Make MakeA8 makeColorType makeColorSpace

---

makeColorType

SkImageInfo makeColorType(SkColorType newColorType) const

Creates Image Info with same Alpha Type, Color Space, width, and height, with Color Type set to newColorType.

Parameters

newColorType

one of: kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType

Return Value

created Image Info

Example

See Also

Make makeAlphaType makeColorSpace

---

makeColorSpace

SkImageInfo makeColorSpace(sk sp<SkColorSpace> cs) const

Creates Image Info with same Alpha Type, Color Type, width, and height, with Color Space set to cs.

Parameters

cs	range of colors; may be nullptr

Return Value

created Image Info

Example

See Also

Make MakeS32 makeAlphaType makeColorType

---

bytesPerPixel

int bytesPerPixel() const

Returns number of bytes per pixel required by Color Type. Returns zero if colorType( is kUnknown_SkColorType.

Return Value

bytes in pixel

Example

kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType

Example Output

color: kUnknown_SkColorType      bytesPerPixel: 0
color: kAlpha_8_SkColorType      bytesPerPixel: 1
color: kRGB_565_SkColorType      bytesPerPixel: 2
color: kARGB_4444_SkColorType    bytesPerPixel: 2
color: kRGBA_8888_SkColorType    bytesPerPixel: 4
color: kRGB_888x_SkColorType     bytesPerPixel: 4
color: kBGRA_8888_SkColorType    bytesPerPixel: 4
color: kRGBA_1010102_SkColorType bytesPerPixel: 4
color: kRGB_101010x_SkColorType  bytesPerPixel: 4
color: kGray_8_SkColorType       bytesPerPixel: 1
color: kRGBA_F16_SkColorType     bytesPerPixel: 8

See Also

width shiftPerPixel SkBitmap::bytesPerPixel

---

shiftPerPixel

int shiftPerPixel() const

Returns bit shift converting row bytes to row pixels. Returns zero for kUnknown_SkColorType.

Return Value

one of: 0, 1, 2, 3; left shift to convert pixels to bytes

Example

kUnknown_SkColorType, kAlpha_8_SkColorType, kRGB_565_SkColorType, kARGB_4444_SkColorType, kRGBA_8888_SkColorType, kRGB_888x_SkColorType, kBGRA_8888_SkColorType, kRGBA_1010102_SkColorType, kRGB_101010x_SkColorType, kGray_8_SkColorType, kRGBA_F16_SkColorType

Example Output

color: kUnknown_SkColorType       shiftPerPixel: 0
color: kAlpha_8_SkColorType       shiftPerPixel: 0
color: kRGB_565_SkColorType       shiftPerPixel: 1
color: kARGB_4444_SkColorType     shiftPerPixel: 1
color: kRGBA_8888_SkColorType     shiftPerPixel: 2
color: kRGB_888x_SkColorType      shiftPerPixel: 2
color: kBGRA_8888_SkColorType     shiftPerPixel: 2
color: kRGBA_1010102_SkColorType  shiftPerPixel: 2
color: kRGB_101010x_SkColorType   shiftPerPixel: 2
color: kGray_8_SkColorType        shiftPerPixel: 0
color: kRGBA_F16_SkColorType      shiftPerPixel: 3

See Also

bytesPerPixel minRowBytes SkBitmap::shiftPerPixel SkPixmap::shiftPerPixel

---

minRowBytes64

uint64_t minRowBytes64() const

Returns minimum bytes per row, computed from pixel width and Color Type, which specifies bytesPerPixel. Bitmap maximum value for row bytes must fit in 31 bits.

Return Value

width times bytesPerPixel as unsigned 64-bit integer

Example

Example Output

RGBA_F16 width 16777216 (0x01000000) OK
RGBA_F16 width 33554432 (0x02000000) OK
RGBA_F16 width 67108864 (0x04000000) OK
RGBA_F16 width 134217728 (0x08000000) OK
RGBA_F16 width 268435456 (0x10000000) too large
RGBA_F16 width 536870912 (0x20000000) too large
RGBA_F16 width 1073741824 (0x40000000) too large
RGBA_F16 width -2147483648 (0x80000000) too large

See Also

minRowBytes computeByteSize computeMinByteSize validRowBytes

---

minRowBytes

size_t minRowBytes() const

Returns minimum bytes per row, computed from pixel width and Color Type, which specifies bytesPerPixel. Bitmap maximum value for row bytes must fit in 31 bits.

Return Value

width times bytesPerPixel as signed 32-bit integer

Example

Example Output

RGBA_F16 width 16777216 (0x01000000) OK
RGBA_F16 width 33554432 (0x02000000) OK
RGBA_F16 width 67108864 (0x04000000) OK
RGBA_F16 width 134217728 (0x08000000) OK
RGBA_F16 width 268435456 (0x10000000) too large
RGBA_F16 width 536870912 (0x20000000) too large
RGBA_F16 width 1073741824 (0x40000000) too large
RGBA_F16 width -2147483648 (0x80000000) too large

See Also

minRowBytes64 computeByteSize computeMinByteSize validRowBytes

---

computeOffset

size_t computeOffset(int x, int y, size_t rowBytes) const

Returns byte offset of pixel from pixel base address.

Asserts in debug build if x or y is outside of bounds. Does not assert if rowBytes is smaller than minRowBytes, even though result may be incorrect.

Parameters

x	column index, zero or greater, and less than width
y	row index, zero or greater, and less than height
rowBytes	size of pixel row or larger

Return Value

offset within pixel array

Example

See Also

height width minRowBytes computeByteSize

---

Operator

SkImageInfo operators inline class member functions with arithmetic equivalents.

Topic	Description
operator!=(const SkImageInfo& other) const	compares Image Info for inequality
operator==(const SkImageInfo& other) const	compares Image Info for equality

operator==

bool operator==(const SkImageInfo& other) _const

Compares Image Info with other, and returns true if width, height, Color Type, Alpha Type, and Color Space are equivalent.

Parameters

other

Image Info to compare

Return Value

true if Image Info equals other

Example

Example Output

info1 != info2
info1 != info2
info1 != info2
info1 == info2

See Also

operator!=(const SkImageInfo& other) const SkColorSpace::Equals

---

operator!=

bool operator!=(const SkImageInfo& other) _const

Compares Image Info with other, and returns true if width, height, Color Type, Alpha Type, and Color Space are not equivalent.

Parameters

other

Image Info to compare

Return Value

true if Image Info is not equal to other

Example

Example Output

info1 != info2
info1 != info2
info1 != info2
info1 == info2

See Also

operator==(const SkImageInfo& other) const SkColorSpace::Equals

---

computeByteSize

size_t computeByteSize(size_t rowBytes) const

Returns storage required by pixel array, given Image Info dimensions, Color Type, and rowBytes. rowBytes is assumed to be at least as large as minRowBytes.

Returns zero if height is zero. Returns SK MaxSizeT if answer exceeds the range of size_t.

Parameters

rowBytes

size of pixel row or larger

Return Value

memory required by pixel buffer

Example

See Also

computeMinByteSize validRowBytes

---

computeMinByteSize

size_t computeMinByteSize() const

Returns storage required by pixel array, given Image Info dimensions, and Color Type. Uses minRowBytes to compute bytes for pixel row.

Returns zero if height is zero. Returns SK MaxSizeT if answer exceeds the range of size_t.

Return Value

least memory required by pixel buffer

Example

See Also

computeByteSize validRowBytes

---

ByteSizeOverflowed

static bool ByteSizeOverflowed(size_t byteSize)

Returns true if byteSize equals SK MaxSizeT. computeByteSize and computeMinByteSize return SK MaxSizeT if size_t can not hold buffer size.

Parameters

byteSize

result of computeByteSize or computeMinByteSize

Return Value

true if computeByteSize or computeMinByteSize result exceeds size_t

Example

Example Output

rowBytes:100000000 size:99999999900000008 overflowed:false
rowBytes:1000000000 size:999999999000000008 overflowed:false
rowBytes:10000000000 size:9999999990000000008 overflowed:false
rowBytes:100000000000 size:18446744073709551615 overflowed:true
rowBytes:1000000000000 size:18446744073709551615 overflowed:true

See Also

computeByteSize computeMinByteSize validRowBytes

---

validRowBytes

bool validRowBytes(size_t rowBytes) const

Returns true if rowBytes is smaller than width times pixel size.

Parameters

rowBytes

size of pixel row or larger

Return Value

true if rowBytes is large enough to contain pixel row

Example

Example Output

validRowBytes(60): false
validRowBytes(64): true
validRowBytes(68): true

See Also

ByteSizeOverflowed computeByteSize computeMinByteSize

---

reset

void reset()

Creates an empty Image Info with kUnknown_SkColorType, kUnknown_SkAlphaType, a width and height of zero, and no Color Space.

Example

Example Output

info == copy
info != reset copy
SkImageInfo() == reset copy

See Also

SkImageInfo()

---

Utility

Topic	Description
ByteSizeOverflowed	checks result of computeByteSize and computeMinByteSize
computeByteSize	returns memory required by pixel buffer with given row bytes
computeMinByteSize	returns least memory required by pixel buffer
computeOffset	returns byte offset within pixel array
validRowBytes	checks if row bytes is large enough to contain pixel row
validate	asserts if Image Info is invalid (debug only)

validate

void validate() const

Asserts if internal values are illegal or inconsistent. Only available if SK_DEBUG is defined at compile time.

See Also

validRowBytes SkBitmap::validate

---