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
Overview Subtopic
| name | description |
|---|---|
| Constructor | functions that construct SkImageInfo |
| Member Function | static functions and member methods |
| Operator | operator overloading methods |
| Related Function | similar methods grouped together |
Constant
| name | description |
|---|
Alpha Type
Enum 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.
Color RGB may have Color Alpha included in each component value; the stored value is the original Color RGB multiplied by Color Alpha. Premultiplied color components improve performance.
Constants
See Also
SkColorType SkColorSpace
Alpha Type Opaque
Use Opaque 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 Opaque but all alpha values are not 1.0, results are undefined.
Example
Alpha Type Premul
Use Premul 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 alphaThe color component must be equal to or smaller than the alpha component, or the results are undefined.
Example
Alpha Type Unpremul
Use Unpremul if stored color components are not divided by the alpha component. Some drawing destinations may not support Unpremul.
Example
Color Type
Color Type Native
Enum SkColorType
Describes how pixel bits encode color. A pixel may be an alpha mask, a gray level, Color RGB, or Color ARGB.
kN32_SkColorType selects the native 32-bit Color ARGB format. On Little_Endian processors, pixels containing 8-bit Color ARGB components pack into 32-bit kBGRA_8888_SkColorType. On Big_Endian processors, pixels pack into 32-bit kRGBA_8888_SkColorType.
Constants
Constants
See Also
SkAlphaType SkColorSpace
Color Type Alpha 8
Alpha 8 is an 8-bit byte pixel encoding that represents transparency. A value of zero is completely transparent; a value of 255 is completely opaque. Bitmap with Alpha 8 pixels does not visibly draw, because its pixels have no color information. The paired SkAlphaType is ignored.
Example
Color Type BGR 565
BGR 565 is a 16-bit word pixel encoding that contains five bits of blue, six bits of green, and five bits of red. BGR 565 is fully opaque as if its Color Alpha was set to one, and should always be paired with kOpaque_SkAlphaType.
Example
Color Type ABGR 4444
ABGR 4444 is a 16-bit word pixel encoding that contains four bits of alpha, four bits of blue, four bits of green, and four bits of red.
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
Color Type RGBA 8888
RGBA 8888 is a 32-bit word pixel encoding that contains eight bits of red, eight bits of green, eight bits of blue, and eight bits of alpha.
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, RGBA 8888 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
Color Type RGB 888x
RGB 888x is a 32-bit word pixel encoding that contains eight bits of red, eight bits of green, eight bits of blue, and eight unused bits. RGB 888x is fully opaque as if its Color Alpha was set to one, and should always be paired with kOpaque_SkAlphaType.
Example
Color Type BGRA 8888
BGRA 8888 is a 32-bit word pixel encoding that contains eight bits of blue, eight bits of green, eight bits of red, and eight bits of alpha.
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 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 255, the drawn result is undefined.
On Little_Endian platforms, BGRA 8888 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
Color Type RGBA 1010102
RGBA 1010102 is a 32-bit word pixel encoding that contains ten bits of red, ten bits of green, ten bits of blue, and two bits of alpha. Possible alpha values are zero: fully transparent; one: 33% opaque; two: 67% opaque; three: fully opaque.
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 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 3, the drawn result is undefined.
Example
Color Type RGB 101010x
Example
Color Type Gray 8
Example
Color Type RGBA F16
Example
YUV ColorSpace
Enum SkYUVColorSpace
Describes the color space a YUV pixel.
Constants
Example
See Also
incomplete
Enum SkDestinationSurfaceColorMode
Constants
Example
See Also
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Struct SkImageInfo
Describes Image dimensions and pixel type. Used for both source images and render-targets (surfaces).
Member Function
| name | description |
|---|---|
| ByteSizeOverflowed | incomplete |
| 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 |
| alphaType | incomplete |
| bounds | incomplete |
| bytesPerPixel | incomplete |
| colorSpace | incomplete |
| colorType | incomplete |
| computeByteSize | incomplete |
| computeMinByteSize | incomplete |
| computeOffset | incomplete |
| dimensions | incomplete |
| flatten | incomplete |
| gammaCloseToSRGB | incomplete |
| height | incomplete |
| isEmpty | incomplete |
| isOpaque | incomplete |
| 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 | incomplete |
| minRowBytes64 | incomplete |
| refColorSpace | incomplete |
| reset | incomplete |
| shiftPerPixel | incomplete |
| unflatten | incomplete |
| validRowBytes | incomplete |
| validate | incomplete |
| width | incomplete |
Related Function
| name | description |
|---|---|
| Property | metrics and attributes |
| Utility | rarely called management functions |
Constructor
| name | 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 | incomplete |
SkImageInfo
Return Value
incomplete
Example
See Also
incomplete
Make
Parameters
Return Value
incomplete
Example
See Also
incomplete
MakeN32
Sets Color Type to kN32_SkColorType.
Parameters
Return Value
incomplete
Example
See Also
incomplete
MakeS32
Creates Image Info marked as sRGB with kN32_SkColorType swizzle.
Parameters
Return Value
incomplete
Example
See Also
incomplete
MakeN32Premul
Sets Color Type to kN32_SkColorType, and the Alpha Type to kPremul_SkAlphaType.
Parameters
Return Value
incomplete
Example
See Also
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Parameters
Return Value
incomplete
Example
See Also
incomplete
MakeA8
Parameters
Return Value
incomplete
Example
See Also
incomplete
MakeUnknown
Parameters
Return Value
incomplete
Example
See Also
incomplete
Return Value
incomplete
Example
See Also
incomplete
Property
| name | description |
|---|---|
| alphaType | incomplete |
| bounds | incomplete |
| bytesPerPixel | incomplete |
| colorSpace | incomplete |
| colorType | incomplete |
| dimensions | incomplete |
| gammaCloseToSRGB | incomplete |
| height | incomplete |
| isEmpty | incomplete |
| isOpaque | incomplete |
| minRowBytes | incomplete |
| minRowBytes64 | incomplete |
| refColorSpace | incomplete |
| shiftPerPixel | incomplete |
| width | incomplete |
width
Return Value
incomplete
Example
See Also
incomplete
height
Return Value
incomplete
Example
See Also
incomplete
colorType
Return Value
incomplete
Example
See Also
incomplete
alphaType
Return Value
incomplete
Example
See Also
incomplete
colorSpace
Return Value
incomplete
Example
See Also
incomplete
refColorSpace
Return Value
incomplete
Example
See Also
incomplete
isEmpty
Return Value
incomplete
Example
See Also
incomplete
isOpaque
Return Value
incomplete
Example
See Also
incomplete
dimensions
Return Value
incomplete
Example
See Also
incomplete
bounds
Return Value
incomplete
Example
See Also
incomplete
gammaCloseToSRGB
Return Value
incomplete
Example
See Also
incomplete
makeWH
Creates Image Info with the same Color Type and Alpha Type as this info, but with the specified width and height.
Parameters
Return Value
incomplete
Example
See Also
incomplete
makeAlphaType
Parameters
Return Value
incomplete
Example
See Also
incomplete
makeColorType
Parameters
Return Value
incomplete
Example
See Also
incomplete
makeColorSpace
Parameters
Return Value
incomplete
Example
See Also
incomplete
bytesPerPixel
Return Value
incomplete
Example
See Also
incomplete
shiftPerPixel
Return Value
incomplete
Example
See Also
incomplete
minRowBytes64
Return Value
incomplete
Example
See Also
incomplete
minRowBytes
Return Value
incomplete
Example
See Also
incomplete
computeOffset
Parameters
Return Value
incomplete
Example
See Also
incomplete
Operator
| name | description |
|---|---|
| operator!=(const SkImageInfo& other) const | incomplete |
| operator==(const SkImageInfo& other) const | incomplete |
operator==
Parameters
Return Value
incomplete
Example
See Also
incomplete
operator!=
Parameters
Return Value
incomplete
Example
See Also
incomplete
unflatten
Parameters
Example
See Also
incomplete
flatten
Parameters
Example
See Also
incomplete
computeByteSize
Returns the size (in bytes) of the image buffer that this info needs, given the specified rowBytes. The rowBytes must be >= this->minRowBytes. if (height == 0) { return 0; } else { return (height - 1) * rowBytes + width * bytes_per_pixel.
If the calculation overflows this returns SK MaxSizeT.
Parameters
Return Value
incomplete
Example
See Also
incomplete
computeMinByteSize
Returns the minimum size (in bytes) of the image buffer that this info needs. If the calculation overflows, or if the height is 0, this returns 0.
Return Value
incomplete
Example
See Also
incomplete
ByteSizeOverflowed
Returns true if the result of computeByteSize (or computeMinByteSize) overflowed
Parameters
Return Value
incomplete
Example
See Also
incomplete
validRowBytes
Parameters
Return Value
incomplete
Example
See Also
incomplete
reset
Example
See Also
incomplete
Utility
| name | description |
|---|---|
| ByteSizeOverflowed | incomplete |
| computeByteSize | incomplete |
| computeMinByteSize | incomplete |
| computeOffset | incomplete |
| flatten | incomplete |
| unflatten | incomplete |
| validRowBytes | incomplete |
| validate | incomplete |
validate
Example
See Also
incomplete