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import "image/png"
Overview
Index
Examples
概观
包png实现了一个PNG图像解码器和编码器。
The PNG specification is at http://www.w3.org/TR/PNG/.
索引
func Decode(r io.Reader) (image.Image, error)
func DecodeConfig(r io.Reader) (image.Config, error)
func Encode(w io.Writer, m image.Image) error
type CompressionLevel
type Encoder
func (enc *Encoder) Encode(w io.Writer, m image.Image) error
type EncoderBuffer
type EncoderBufferPool
type FormatError
func (e FormatError) Error() string
type UnsupportedError
func (e UnsupportedError) Error() string
例子
解码编码
包文件
paeth.go reader.go writer.go
func Decode
func Decode(r io.Reader) (image.Image, error)
解码从r读取一个PNG图像并将其作为image.Image返回。返回的图像类型取决于PNG内容。
例子
代码:
// This example uses png.Decode which can only decode PNG images.// Consider using the general image.Decode as it can sniff and decode any registered image format.img, err := png.Decode(gopherPNG())if err != nil {
log.Fatal(err)}levels := []string{" ", "░", "▒", "▓", "█"}for y := img.Bounds().Min.Y; y < img.Bounds().Max.Y; y++ { for x := img.Bounds().Min.X; x < img.Bounds().Max.X; x++ {
c := color.GrayModel.Convert(img.At(x, y)).(color.Gray)
level := c.Y / 51 // 51 * 5 = 255 if level == 5 {
level-- }
fmt.Print(levels[level]) }
fmt.Print("\n")}func DecodeConfig
func DecodeConfig(r io.Reader) (image.Config, error)
DecodeConfig返回PNG图像的颜色模型和尺寸，而不用解码整个图像。
func Encode
func Encode(w io.Writer, m image.Image) error
Encode将图像m以PNG格式写入w。任何图像都可能被编码，但不是image.NRGBA的图像可能会被损坏编码。
例子
package mainimport ("image""image/color""image/png""log""os")func main() {const width, height = 256, 256// Create a colored image of the given width and height.
img := image.NewNRGBA(image.Rect(0, 0, width, height))for y := 0; y < height; y++ {for x := 0; x < width; x++ {
img.Set(x, y, color.NRGBA{
R: uint8((x + y) & 255),
G: uint8((x + y) << 1 & 255),
B: uint8((x + y) << 2 & 255),
A: 255,})}}
f, err := os.Create("image.png")if err != nil {
log.Fatal(err)}if err := png.Encode(f, img); err != nil {
f.Close()
log.Fatal(err)}if err := f.Close(); err != nil {
log.Fatal(err)}}type CompressionLevel
type CompressionLevel int
const ( DefaultCompression CompressionLevel = 0 NoCompression CompressionLevel = -1 BestSpeed CompressionLevel = -2 BestCompression CompressionLevel = -3)
type Encoder
编码器配置编码PNG图像。
type Encoder struct {
CompressionLevel CompressionLevel // BufferPool optionally specifies a buffer pool to get temporary // EncoderBuffers when encoding an image.
BufferPool EncoderBufferPool}func (*Encoder) Encode
func (enc *Encoder) Encode(w io.Writer, m image.Image) error
编码将图像m以PNG格式写入w。
type EncoderBuffer
EncoderBuffer保存用于编码PNG图像的缓冲区。
type EncoderBuffer encoder
type EncoderBufferPool
EncoderBufferPool是用于获取和返回EncoderBuffer结构的临时实例的接口。这可以用于编码多个图像时重用缓冲区。
type EncoderBufferPool interface { Get() *EncoderBuffer Put(*EncoderBuffer)}type FormatError
FormatError报告输入不是有效的PNG。
type FormatError string
func (FormatError) Error
func (e FormatError) Error() string
type UnsupportedError
UnsupportedError报告输入使用有效但未实现的PNG功能。
type UnsupportedError string
func (UnsupportedError) Error
func (e UnsupportedError) Error() string