import "image/png"
Package png implements a PNG image decoder and encoder.
The PNG specification is at https://www.w3.org/TR/PNG/.
func Decode(r io.Reader) (image.Image, error)
Decode reads a PNG image from r and returns it as an image.Image. The type of Image returned depends on the PNG contents.
Code:
// 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(r io.Reader) (image.Config, error)
DecodeConfig returns the color model and dimensions of a PNG image without decoding the entire image.
func Encode(w io.Writer, m image.Image) error
Encode writes the Image m to w in PNG format. Any Image may be encoded, but images that are not image.NRGBA might be encoded lossily.
Code:
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 int
const (
DefaultCompression CompressionLevel = 0
NoCompression CompressionLevel = -1
BestSpeed CompressionLevel = -2
BestCompression CompressionLevel = -3
)
type Encoder struct {
CompressionLevel CompressionLevel
// BufferPool optionally specifies a buffer pool to get temporary
// EncoderBuffers when encoding an image.
BufferPool EncoderBufferPool
}
Encoder configures encoding PNG images.
func (enc *Encoder) Encode(w io.Writer, m image.Image) error
Encode writes the Image m to w in PNG format.
type EncoderBuffer encoder
EncoderBuffer holds the buffers used for encoding PNG images.
type EncoderBufferPool interface {
Get() *EncoderBuffer
Put(*EncoderBuffer)
}
EncoderBufferPool is an interface for getting and returning temporary instances of the EncoderBuffer struct. This can be used to reuse buffers when encoding multiple images.
type FormatError string
A FormatError reports that the input is not a valid PNG.
func (e FormatError) Error() string
type UnsupportedError string
An UnsupportedError reports that the input uses a valid but unimplemented PNG feature.
func (e UnsupportedError) Error() string