package png

Import Path
	image/png (on go.dev)

Dependency Relation
	imports 10 packages, and imported by 0 packages


Involved Source Files

	    paeth.go
	
		Package png implements a PNG image decoder and encoder.
		
		The PNG specification is at https://www.w3.org/TR/PNG/.

	    writer.go


Code Examples

	
		package main
		
		import (
			"encoding/base64"
			"fmt"
			"image/color"
			"image/png"
			"io"
			"log"
			"strings"
		)
		
		const gopher = `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`
		
		// gopherPNG creates an io.Reader by decoding the base64 encoded image data string in the gopher constant.
		func gopherPNG() io.Reader { return base64.NewDecoder(base64.StdEncoding, strings.NewReader(gopher)) }
		
		func main() {
			// 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")
			}
		}

	
		package main
		
		import (
			"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)
			}
		}




Package-Level Type Names (total 6)


	/* sort by:  |  */
	
		CompressionLevel indicates the compression level.

		
			const BestCompression
			const BestSpeed
			const DefaultCompression
			const NoCompression


	
		Encoder configures encoding PNG images.

		
			
				BufferPool optionally specifies a buffer pool to get temporary
				EncoderBuffers when encoding an image.

			CompressionLevel CompressionLevel
		
			
				Encode writes the Image m to w in PNG format.



	
		EncoderBuffer holds the buffers used for encoding PNG images.

		
			func EncoderBufferPool.Get() *EncoderBuffer
		
			func EncoderBufferPool.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.

		
			( EncoderBufferPool) Get() *EncoderBuffer
			( EncoderBufferPool) Put(*EncoderBuffer)


	
		A FormatError reports that the input is not a valid PNG.

		
			( FormatError) Error() string
		
			 FormatError : error


	
		An UnsupportedError reports that the input uses a valid but unimplemented PNG feature.

		
			( UnsupportedError) Error() string
		
			 UnsupportedError : error




Package-Level Functions (total 3)


	
		Decode reads a PNG image from r and returns it as an image.Image.
		The type of Image returned depends on the PNG contents.


	
		DecodeConfig returns the color model and dimensions of a PNG image without
		decoding the entire image.


	
		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.




Package-Level Constants (total 4)