Documentation
¶
Overview ¶
Package image implements a basic 2-D image library.
The fundamental interface is called Image. An Image contains colors, which are described in the image/color package.
Values of the Image interface are created either by calling functions such as NewRGBA and NewPaletted, or by calling Decode on an io.Reader containing image data in a format such as GIF, JPEG or PNG. Decoding any particular image format requires the prior registration of a decoder function. Registration is typically automatic as a side effect of initializing that format's package so that, to decode a PNG image, it suffices to have
import _ "image/png"
in a program's main package. The _ means to import a package purely for its initialization side effects.
See "The Go image package" for more details: https://golang.org/doc/articles/image_package.html
Security Considerations ¶
The image package can be used to parse arbitrarily large images, which can cause resource exhaustion on machines which do not have enough memory to store them. When operating on arbitrary images, DecodeConfig should be called before Decode, so that the program can decide whether the image, as defined in the returned header, can be safely decoded with the available resources. A call to Decode which produces an extremely large image, as defined in the header returned by DecodeConfig, is not considered a security issue, regardless of whether the image is itself malformed or not. A call to DecodeConfig which returns a header which does not match the image returned by Decode may be considered a security issue, and should be reported per the Go Security Policy.
Example ¶
package main
import (
"encoding/base64"
"fmt"
"image"
"log"
"strings"
// Packages image/gif and image/jpeg are not used explicitly in the code
// below, but are imported for their initialization side-effects, which
// allow image.Decode and image.DecodeConfig to understand GIF and JPEG
// formatted images. Uncomment the line below to also understand PNG:
// _ "image/png"
_ "image/gif"
_ "image/jpeg"
)
func main() {
// Decode the JPEG data. If reading from file, create a reader with
//
// reader, err := os.Open("testdata/video-001.q50.420.jpeg")
// if err != nil {
// log.Fatal(err)
// }
// defer reader.Close()
reader := base64.NewDecoder(base64.StdEncoding, strings.NewReader(data))
m, _, err := image.Decode(reader)
if err != nil {
log.Fatal(err)
}
bounds := m.Bounds()
// Calculate a 16-bin histogram for m's red, green, blue and alpha components.
//
// An image's bounds do not necessarily start at (0, 0), so the two loops start
// at bounds.Min.Y and bounds.Min.X. Looping over Y first and X second is more
// likely to result in better memory access patterns than X first and Y second.
var histogram [16][4]int
for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
for x := bounds.Min.X; x < bounds.Max.X; x++ {
r, g, b, a := m.At(x, y).RGBA()
// A color's RGBA method returns values in the range [0, 65535].
// Shifting by 12 reduces this to the range [0, 15].
histogram[r>>12][0]++
histogram[g>>12][1]++
histogram[b>>12][2]++
histogram[a>>12][3]++
}
}
// Print the results.
fmt.Printf("%-14s %6s %6s %6s %6s\n", "bin", "red", "green", "blue", "alpha")
for i, x := range histogram {
fmt.Printf("0x%04x-0x%04x: %6d %6d %6d %6d\n", i<<12, (i+1)<<12-1, x[0], x[1], x[2], x[3])
}
}
const data = `
/9j/4AAQSkZJRgABAQIAHAAcAAD/2wBDABALDA4MChAODQ4SERATGCgaGBYWGDEjJR0oOjM9PDkzODdA
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`
Output: bin red green blue alpha 0x0000-0x0fff: 362 793 7245 0 0x1000-0x1fff: 648 2963 1036 0 0x2000-0x2fff: 1072 2301 977 0 0x3000-0x3fff: 819 2266 982 0 0x4000-0x4fff: 537 1303 541 0 0x5000-0x5fff: 321 964 261 0 0x6000-0x6fff: 321 375 177 0 0x7000-0x7fff: 599 278 213 0 0x8000-0x8fff: 3478 228 275 0 0x9000-0x9fff: 2260 233 328 0 0xa000-0xafff: 921 282 374 0 0xb000-0xbfff: 322 335 395 0 0xc000-0xcfff: 228 388 299 0 0xd000-0xdfff: 261 415 277 0 0xe000-0xefff: 516 423 297 0 0xf000-0xffff: 2785 1903 1773 15450
Example (DecodeConfig) ¶
package main
import (
"encoding/base64"
"fmt"
"image"
"log"
"strings"
// Packages image/gif and image/jpeg are not used explicitly in the code
// below, but are imported for their initialization side-effects, which
// allow image.Decode and image.DecodeConfig to understand GIF and JPEG
// formatted images. Uncomment the line below to also understand PNG:
// _ "image/png"
_ "image/gif"
_ "image/jpeg"
)
func main() {
reader := base64.NewDecoder(base64.StdEncoding, strings.NewReader(data))
config, format, err := image.DecodeConfig(reader)
if err != nil {
log.Fatal(err)
}
fmt.Println("Width:", config.Width, "Height:", config.Height, "Format:", format)
}
const data = `
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lIJnU8OfxPWo5inBokmtQTmM4OOh71b0q6vbFmWCbaxHyqQGAP0PT8KhSTzVyo5ocSKA5VfTOTmqsmRd
pl99XjPzThzK3zOeOSeveirNmkgg/fIpYsTkYORxRXmzlTjJqx6EVUcU7mhkKCzdAK59QI9zYxtG1fYU
UVtgtmY4nZEa8Ak9aqFv3rfSiiu1nMeifDv/AJF+T/r4f+QrqqKKQwzQenNFFMCOKFIgNuThdoJ5OPSk
ubeK6t3gnXdG4wwziiii/UTKMOg6dbzJLFE4dSCP3rEdeOM8805tDsGMvySgSsS6rM6gk9eAcUUVftZt
3uyVGNthuq3Eei6DK8H7sRR7YuMgHtXkc8rzTNLM26RyWY+p70UVnLY0iEsUipG7rhZBlDkc1HgYoorM
0HwyBXGeRjmrcUhMg2ghezd//rUUVcTKW5s2jZtY/QDaOKKKK8ip8bPRj8KP/9k=
`
Output:
Index ¶
- Variables
- func RegisterFormat(name, magic string, decode func(io.Reader) (Image, error), ...)
- type Alpha
- func (p *Alpha) AlphaAt(x, y int) color.Alpha
- func (p *Alpha) At(x, y int) color.Color
- func (p *Alpha) Bounds() Rectangle
- func (p *Alpha) ColorModel() color.Model
- func (p *Alpha) Opaque() bool
- func (p *Alpha) PixOffset(x, y int) int
- func (p *Alpha) RGBA64At(x, y int) color.RGBA64
- func (p *Alpha) Set(x, y int, c color.Color)
- func (p *Alpha) SetAlpha(x, y int, c color.Alpha)
- func (p *Alpha) SetRGBA64(x, y int, c color.RGBA64)
- func (p *Alpha) SubImage(r Rectangle) Image
- type Alpha16
- func (p *Alpha16) Alpha16At(x, y int) color.Alpha16
- func (p *Alpha16) At(x, y int) color.Color
- func (p *Alpha16) Bounds() Rectangle
- func (p *Alpha16) ColorModel() color.Model
- func (p *Alpha16) Opaque() bool
- func (p *Alpha16) PixOffset(x, y int) int
- func (p *Alpha16) RGBA64At(x, y int) color.RGBA64
- func (p *Alpha16) Set(x, y int, c color.Color)
- func (p *Alpha16) SetAlpha16(x, y int, c color.Alpha16)
- func (p *Alpha16) SetRGBA64(x, y int, c color.RGBA64)
- func (p *Alpha16) SubImage(r Rectangle) Image
- type CMYK
- func (p *CMYK) At(x, y int) color.Color
- func (p *CMYK) Bounds() Rectangle
- func (p *CMYK) CMYKAt(x, y int) color.CMYK
- func (p *CMYK) ColorModel() color.Model
- func (p *CMYK) Opaque() bool
- func (p *CMYK) PixOffset(x, y int) int
- func (p *CMYK) RGBA64At(x, y int) color.RGBA64
- func (p *CMYK) Set(x, y int, c color.Color)
- func (p *CMYK) SetCMYK(x, y int, c color.CMYK)
- func (p *CMYK) SetRGBA64(x, y int, c color.RGBA64)
- func (p *CMYK) SubImage(r Rectangle) Image
- type Config
- type Gray
- func (p *Gray) At(x, y int) color.Color
- func (p *Gray) Bounds() Rectangle
- func (p *Gray) ColorModel() color.Model
- func (p *Gray) GrayAt(x, y int) color.Gray
- func (p *Gray) Opaque() bool
- func (p *Gray) PixOffset(x, y int) int
- func (p *Gray) RGBA64At(x, y int) color.RGBA64
- func (p *Gray) Set(x, y int, c color.Color)
- func (p *Gray) SetGray(x, y int, c color.Gray)
- func (p *Gray) SetRGBA64(x, y int, c color.RGBA64)
- func (p *Gray) SubImage(r Rectangle) Image
- type Gray16
- func (p *Gray16) At(x, y int) color.Color
- func (p *Gray16) Bounds() Rectangle
- func (p *Gray16) ColorModel() color.Model
- func (p *Gray16) Gray16At(x, y int) color.Gray16
- func (p *Gray16) Opaque() bool
- func (p *Gray16) PixOffset(x, y int) int
- func (p *Gray16) RGBA64At(x, y int) color.RGBA64
- func (p *Gray16) Set(x, y int, c color.Color)
- func (p *Gray16) SetGray16(x, y int, c color.Gray16)
- func (p *Gray16) SetRGBA64(x, y int, c color.RGBA64)
- func (p *Gray16) SubImage(r Rectangle) Image
- type Image
- type NRGBA
- func (p *NRGBA) At(x, y int) color.Color
- func (p *NRGBA) Bounds() Rectangle
- func (p *NRGBA) ColorModel() color.Model
- func (p *NRGBA) NRGBAAt(x, y int) color.NRGBA
- func (p *NRGBA) Opaque() bool
- func (p *NRGBA) PixOffset(x, y int) int
- func (p *NRGBA) RGBA64At(x, y int) color.RGBA64
- func (p *NRGBA) Set(x, y int, c color.Color)
- func (p *NRGBA) SetNRGBA(x, y int, c color.NRGBA)
- func (p *NRGBA) SetRGBA64(x, y int, c color.RGBA64)
- func (p *NRGBA) SubImage(r Rectangle) Image
- type NRGBA64
- func (p *NRGBA64) At(x, y int) color.Color
- func (p *NRGBA64) Bounds() Rectangle
- func (p *NRGBA64) ColorModel() color.Model
- func (p *NRGBA64) NRGBA64At(x, y int) color.NRGBA64
- func (p *NRGBA64) Opaque() bool
- func (p *NRGBA64) PixOffset(x, y int) int
- func (p *NRGBA64) RGBA64At(x, y int) color.RGBA64
- func (p *NRGBA64) Set(x, y int, c color.Color)
- func (p *NRGBA64) SetNRGBA64(x, y int, c color.NRGBA64)
- func (p *NRGBA64) SetRGBA64(x, y int, c color.RGBA64)
- func (p *NRGBA64) SubImage(r Rectangle) Image
- type NYCbCrA
- func (p *NYCbCrA) AOffset(x, y int) int
- func (p *NYCbCrA) At(x, y int) color.Color
- func (p *NYCbCrA) ColorModel() color.Model
- func (p *NYCbCrA) NYCbCrAAt(x, y int) color.NYCbCrA
- func (p *NYCbCrA) Opaque() bool
- func (p *NYCbCrA) RGBA64At(x, y int) color.RGBA64
- func (p *NYCbCrA) SubImage(r Rectangle) Image
- type Paletted
- func (p *Paletted) At(x, y int) color.Color
- func (p *Paletted) Bounds() Rectangle
- func (p *Paletted) ColorIndexAt(x, y int) uint8
- func (p *Paletted) ColorModel() color.Model
- func (p *Paletted) Opaque() bool
- func (p *Paletted) PixOffset(x, y int) int
- func (p *Paletted) RGBA64At(x, y int) color.RGBA64
- func (p *Paletted) Set(x, y int, c color.Color)
- func (p *Paletted) SetColorIndex(x, y int, index uint8)
- func (p *Paletted) SetRGBA64(x, y int, c color.RGBA64)
- func (p *Paletted) SubImage(r Rectangle) Image
- type PalettedImage
- type Point
- type RGBA
- func (p *RGBA) At(x, y int) color.Color
- func (p *RGBA) Bounds() Rectangle
- func (p *RGBA) ColorModel() color.Model
- func (p *RGBA) Opaque() bool
- func (p *RGBA) PixOffset(x, y int) int
- func (p *RGBA) RGBA64At(x, y int) color.RGBA64
- func (p *RGBA) RGBAAt(x, y int) color.RGBA
- func (p *RGBA) Set(x, y int, c color.Color)
- func (p *RGBA) SetRGBA(x, y int, c color.RGBA)
- func (p *RGBA) SetRGBA64(x, y int, c color.RGBA64)
- func (p *RGBA) SubImage(r Rectangle) Image
- type RGBA64
- func (p *RGBA64) At(x, y int) color.Color
- func (p *RGBA64) Bounds() Rectangle
- func (p *RGBA64) ColorModel() color.Model
- func (p *RGBA64) Opaque() bool
- func (p *RGBA64) PixOffset(x, y int) int
- func (p *RGBA64) RGBA64At(x, y int) color.RGBA64
- func (p *RGBA64) Set(x, y int, c color.Color)
- func (p *RGBA64) SetRGBA64(x, y int, c color.RGBA64)
- func (p *RGBA64) SubImage(r Rectangle) Image
- type RGBA64Image
- type Rectangle
- func (r Rectangle) Add(p Point) Rectangle
- func (r Rectangle) At(x, y int) color.Color
- func (r Rectangle) Bounds() Rectangle
- func (r Rectangle) Canon() Rectangle
- func (r Rectangle) ColorModel() color.Model
- func (r Rectangle) Dx() int
- func (r Rectangle) Dy() int
- func (r Rectangle) Empty() bool
- func (r Rectangle) Eq(s Rectangle) bool
- func (r Rectangle) In(s Rectangle) bool
- func (r Rectangle) Inset(n int) Rectangle
- func (r Rectangle) Intersect(s Rectangle) Rectangle
- func (r Rectangle) Overlaps(s Rectangle) bool
- func (r Rectangle) RGBA64At(x, y int) color.RGBA64
- func (r Rectangle) Size() Point
- func (r Rectangle) String() string
- func (r Rectangle) Sub(p Point) Rectangle
- func (r Rectangle) Union(s Rectangle) Rectangle
- type Uniform
- func (c *Uniform) At(x, y int) color.Color
- func (c *Uniform) Bounds() Rectangle
- func (c *Uniform) ColorModel() color.Model
- func (c *Uniform) Convert(color.Color) color.Color
- func (c *Uniform) Opaque() bool
- func (c *Uniform) RGBA() (r, g, b, a uint32)
- func (c *Uniform) RGBA64At(x, y int) color.RGBA64
- type YCbCr
- func (p *YCbCr) At(x, y int) color.Color
- func (p *YCbCr) Bounds() Rectangle
- func (p *YCbCr) COffset(x, y int) int
- func (p *YCbCr) ColorModel() color.Model
- func (p *YCbCr) Opaque() bool
- func (p *YCbCr) RGBA64At(x, y int) color.RGBA64
- func (p *YCbCr) SubImage(r Rectangle) Image
- func (p *YCbCr) YCbCrAt(x, y int) color.YCbCr
- func (p *YCbCr) YOffset(x, y int) int
- type YCbCrSubsampleRatio
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var ( // Black is an opaque black uniform image. Black = NewUniform(color.Black) // White is an opaque white uniform image. White = NewUniform(color.White) // Transparent is a fully transparent uniform image. Transparent = NewUniform(color.Transparent) // Opaque is a fully opaque uniform image. Opaque = NewUniform(color.Opaque) )
var ErrFormat = errors.New("image: unknown format")
ErrFormat indicates that decoding encountered an unknown format.
Functions ¶
func RegisterFormat ¶
func RegisterFormat(name, magic string, decode func(io.Reader) (Image, error), decodeConfig func(io.Reader) (Config, error))
RegisterFormat registers an image format for use by Decode. Name is the name of the format, like "jpeg" or "png". Magic is the magic prefix that identifies the format's encoding. The magic string can contain "?" wildcards that each match any one byte. Decode is the function that decodes the encoded image. DecodeConfig is the function that decodes just its configuration.
Types ¶
type Alpha ¶
type Alpha struct {
// Pix holds the image's pixels, as alpha values. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*1].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
}
Alpha is an in-memory image whose At method returns color.Alpha values.
func (*Alpha) ColorModel ¶
type Alpha16 ¶
type Alpha16 struct {
// Pix holds the image's pixels, as alpha values in big-endian format. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*2].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
}
Alpha16 is an in-memory image whose At method returns color.Alpha16 values.
func NewAlpha16 ¶
NewAlpha16 returns a new Alpha16 image with the given bounds.
func (*Alpha16) ColorModel ¶
type CMYK ¶ added in go1.5
type CMYK struct {
// Pix holds the image's pixels, in C, M, Y, K order. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*4].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
}
CMYK is an in-memory image whose At method returns color.CMYK values.
func (*CMYK) ColorModel ¶ added in go1.5
func (*CMYK) Opaque ¶ added in go1.5
Opaque scans the entire image and reports whether it is fully opaque.
type Config ¶
Config holds an image's color model and dimensions.
func DecodeConfig ¶
DecodeConfig decodes the color model and dimensions of an image that has been encoded in a registered format. The string returned is the format name used during format registration. Format registration is typically done by an init function in the codec-specific package.
DecodeConfig reads only format headers and does not allocate a full-size pixel buffer, so it can be used to check dimensions before calling Decode.
type Gray ¶
type Gray struct {
// Pix holds the image's pixels, as gray values. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*1].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
}
Gray is an in-memory image whose At method returns color.Gray values.
func (*Gray) ColorModel ¶
type Gray16 ¶
type Gray16 struct {
// Pix holds the image's pixels, as gray values in big-endian format. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*2].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
}
Gray16 is an in-memory image whose At method returns color.Gray16 values.
func (*Gray16) ColorModel ¶
type Image ¶
type Image interface {
// ColorModel returns the Image's color model.
ColorModel() color.Model
// Bounds returns the domain for which At can return non-zero color.
// The bounds do not necessarily contain the point (0, 0).
Bounds() Rectangle
// At returns the color of the pixel at (x, y).
// At(Bounds().Min.X, Bounds().Min.Y) returns the upper-left pixel of the grid.
// At(Bounds().Max.X-1, Bounds().Max.Y-1) returns the lower-right one.
At(x, y int) color.Color
}
Image is a finite rectangular grid of color.Color values taken from a color model.
func Decode ¶
Decode decodes an image that has been encoded in a registered format. The string returned is the format name used during format registration. Format registration is typically done by an init function in the codec- specific package.
Decoding may allocate memory proportional to the width and height in the image header before all pixel data is consumed or validated. When decoding untrusted input, call DecodeConfig first to inspect dimensions and reject images that would exceed resource limits; see the "Security Considerations" section in the image package documentation.
Example (Untrusted) ¶
ExampleDecode_untrusted demonstrates decoding an untrusted image file in two steps so that unexpectedly large memory allocations can be safely avoided.
package main
import (
"bytes"
"fmt"
"image"
"log"
// Packages image/gif and image/jpeg are not used explicitly in the code
// below, but are imported for their initialization side-effects, which
// allow image.Decode and image.DecodeConfig to understand GIF and JPEG
// formatted images. Uncomment the line below to also understand PNG:
// _ "image/png"
_ "image/gif"
_ "image/jpeg"
)
func main() {
// This GIF data is a valid 1x1 image (layout matches package gif tests).
gifData := []byte{
'G', 'I', 'F', '8', '9', 'a',
1, 0, 1, 0,
128, 0, 0,
0, 0, 0, 1, 1, 1,
0x21, 0xf9, 0x04, 0x00, 0x00, 0x00, 0xff, 0x00,
0x2c,
0x00, 0x00, 0x00, 0x00,
0x01, 0x00, 0x01, 0x00,
0x00,
0x02, 0x02, 0x4c, 0x01, 0x00,
0x3b,
}
cfg, _, err := image.DecodeConfig(bytes.NewReader(gifData))
if err != nil {
log.Fatal(err)
}
// Use int64 to avoid overflow on 32-bit platforms.
const maxPixels = 10000
if int64(cfg.Width)*int64(cfg.Height) > maxPixels {
fmt.Println("rejected: dimensions too large")
return
}
m, _, err := image.Decode(bytes.NewReader(gifData))
if err != nil {
log.Fatal(err)
}
fmt.Println("decoded", m.Bounds().Dx(), m.Bounds().Dy())
}
Output: decoded 1 1
type NRGBA ¶
type NRGBA struct {
// Pix holds the image's pixels, in R, G, B, A order. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*4].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
}
NRGBA is an in-memory image whose At method returns color.NRGBA values.
func (*NRGBA) ColorModel ¶
type NRGBA64 ¶
type NRGBA64 struct {
// Pix holds the image's pixels, in R, G, B, A order and big-endian format. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*8].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
}
NRGBA64 is an in-memory image whose At method returns color.NRGBA64 values.
func NewNRGBA64 ¶
NewNRGBA64 returns a new NRGBA64 image with the given bounds.
func (*NRGBA64) ColorModel ¶
type NYCbCrA ¶ added in go1.6
NYCbCrA is an in-memory image of non-alpha-premultiplied Y'CbCr-with-alpha colors. A and AStride are analogous to the Y and YStride fields of the embedded YCbCr.
func NewNYCbCrA ¶ added in go1.6
func NewNYCbCrA(r Rectangle, subsampleRatio YCbCrSubsampleRatio) *NYCbCrA
NewNYCbCrA returns a new NYCbCrA image with the given bounds and subsample ratio.
func (*NYCbCrA) AOffset ¶ added in go1.6
AOffset returns the index of the first element of A that corresponds to the pixel at (x, y).
func (*NYCbCrA) ColorModel ¶ added in go1.6
type Paletted ¶
type Paletted struct {
// Pix holds the image's pixels, as palette indices. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*1].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
// Palette is the image's palette.
Palette color.Palette
}
Paletted is an in-memory image of uint8 indices into a given palette.
func NewPaletted ¶
NewPaletted returns a new Paletted image with the given width, height and palette.
func (*Paletted) ColorIndexAt ¶
func (*Paletted) ColorModel ¶
func (*Paletted) PixOffset ¶
PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).
func (*Paletted) SetColorIndex ¶
type PalettedImage ¶
type PalettedImage interface {
// ColorIndexAt returns the palette index of the pixel at (x, y).
ColorIndexAt(x, y int) uint8
Image
}
PalettedImage is an image whose colors may come from a limited palette. If m is a PalettedImage and m.ColorModel() returns a color.Palette p, then m.At(x, y) should be equivalent to p[m.ColorIndexAt(x, y)]. If m's color model is not a color.Palette, then ColorIndexAt's behavior is undefined.
type Point ¶
type Point struct {
X, Y int
}
A Point is an X, Y coordinate pair. The axes increase right and down.
func (Point) Mod ¶
Mod returns the point q in r such that p.X-q.X is a multiple of r's width and p.Y-q.Y is a multiple of r's height.
type RGBA ¶
type RGBA struct {
// Pix holds the image's pixels, in R, G, B, A order. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*4].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
}
RGBA is an in-memory image whose At method returns color.RGBA values.
func (*RGBA) ColorModel ¶
type RGBA64 ¶
type RGBA64 struct {
// Pix holds the image's pixels, in R, G, B, A order and big-endian format. The pixel at
// (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*8].
Pix []uint8
// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
Stride int
// Rect is the image's bounds.
Rect Rectangle
}
RGBA64 is an in-memory image whose At method returns color.RGBA64 values.
func (*RGBA64) ColorModel ¶
type RGBA64Image ¶ added in go1.17
type RGBA64Image interface {
// RGBA64At returns the RGBA64 color of the pixel at (x, y). It is
// equivalent to calling At(x, y).RGBA() and converting the resulting
// 32-bit return values to a color.RGBA64, but it can avoid allocations
// from converting concrete color types to the color.Color interface type.
RGBA64At(x, y int) color.RGBA64
Image
}
RGBA64Image is an Image whose pixels can be converted directly to a color.RGBA64.
type Rectangle ¶
type Rectangle struct {
Min, Max Point
}
A Rectangle contains the points with Min.X <= X < Max.X, Min.Y <= Y < Max.Y. It is well-formed if Min.X <= Max.X and likewise for Y. Points are always well-formed. A rectangle's methods always return well-formed outputs for well-formed inputs.
A Rectangle is also an Image whose bounds are the rectangle itself. At returns color.Opaque for points in the rectangle and color.Transparent otherwise.
func Rect ¶
Rect is shorthand for Rectangle{Pt(x0, y0), Pt(x1, y1)}. The returned rectangle has minimum and maximum coordinates swapped if necessary so that it is well-formed.
func (Rectangle) Canon ¶
Canon returns the canonical version of r. The returned rectangle has minimum and maximum coordinates swapped if necessary so that it is well-formed.
func (Rectangle) ColorModel ¶ added in go1.5
ColorModel implements the Image interface.
func (Rectangle) Eq ¶
Eq reports whether r and s contain the same set of points. All empty rectangles are considered equal.
func (Rectangle) Inset ¶
Inset returns the rectangle r inset by n, which may be negative. If either of r's dimensions is less than 2*n then an empty rectangle near the center of r will be returned.
func (Rectangle) Intersect ¶
Intersect returns the largest rectangle contained by both r and s. If the two rectangles do not overlap then the zero rectangle will be returned.
func (Rectangle) RGBA64At ¶ added in go1.17
RGBA64At implements the RGBA64Image interface.
type Uniform ¶
Uniform is an infinite-sized Image of uniform color. It implements the color.Color, color.Model, and Image interfaces.
func NewUniform ¶
NewUniform returns a new Uniform image of the given color.
func (*Uniform) ColorModel ¶
type YCbCr ¶
type YCbCr struct {
Y, Cb, Cr []uint8
YStride int
CStride int
SubsampleRatio YCbCrSubsampleRatio
Rect Rectangle
}
YCbCr is an in-memory image of Y'CbCr colors. There is one Y sample per pixel, but each Cb and Cr sample can span one or more pixels. YStride is the Y slice index delta between vertically adjacent pixels. CStride is the Cb and Cr slice index delta between vertically adjacent pixels that map to separate chroma samples. It is not an absolute requirement, but YStride and len(Y) are typically multiples of 8, and:
For 4:4:4, CStride == YStride/1 && len(Cb) == len(Cr) == len(Y)/1. For 4:2:2, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/2. For 4:2:0, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/4. For 4:4:0, CStride == YStride/1 && len(Cb) == len(Cr) == len(Y)/2. For 4:1:1, CStride == YStride/4 && len(Cb) == len(Cr) == len(Y)/4. For 4:1:0, CStride == YStride/4 && len(Cb) == len(Cr) == len(Y)/8.
func NewYCbCr ¶
func NewYCbCr(r Rectangle, subsampleRatio YCbCrSubsampleRatio) *YCbCr
NewYCbCr returns a new YCbCr image with the given bounds and subsample ratio.
func (*YCbCr) COffset ¶
COffset returns the index of the first element of Cb or Cr that corresponds to the pixel at (x, y).
func (*YCbCr) ColorModel ¶
type YCbCrSubsampleRatio ¶
type YCbCrSubsampleRatio int
YCbCrSubsampleRatio is the chroma subsample ratio used in a YCbCr image.
const ( YCbCrSubsampleRatio444 YCbCrSubsampleRatio = iota YCbCrSubsampleRatio422 YCbCrSubsampleRatio420 YCbCrSubsampleRatio440 YCbCrSubsampleRatio411 YCbCrSubsampleRatio410 )
func (YCbCrSubsampleRatio) String ¶
func (s YCbCrSubsampleRatio) String() string
Source Files
Directories
¶
| Path | Synopsis |
|---|---|
|
Package color implements a basic color library.
|
Package color implements a basic color library. |
|
palette
Package palette provides standard color palettes.
|
Package palette provides standard color palettes. |
|
Package draw provides image composition functions.
|
Package draw provides image composition functions. |
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Package gif implements a GIF image decoder and encoder.
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Package gif implements a GIF image decoder and encoder. |
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internal
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imageutil
Package imageutil contains code shared by image-related packages.
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Package imageutil contains code shared by image-related packages. |
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Package jpeg implements a JPEG image decoder and encoder.
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Package jpeg implements a JPEG image decoder and encoder. |
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Package png implements a PNG image decoder and encoder.
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Package png implements a PNG image decoder and encoder. |