Golang image.png.Encoder.Encode function and CompressionLevel type example

package image/png

Golang image.png.Encoder.Encode function and CompressionLevel type usage example

 package main

 import (
 "flag"
 "fmt"
 "image"
 "image/color"
 "image/draw"
 "image/png"
 "math/rand"
 "os"
 "time"
 )

 func main() {
 flag.Parse()
 rand.Seed(time.Now().UTC().UnixNano())

 out, err := os.Create("./output.png")
 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 // generate some QR code look a like image

 imgRect := image.Rect(0, 0, 100, 100)
 img := image.NewGray(imgRect)
 draw.Draw(img, img.Bounds(), &image.Uniform{color.White}, image.ZP, draw.Src)
 for y := 0; y < 100; y += 10 {
 for x := 0; x < 100; x += 10 {
 fill := &image.Uniform{color.Black}
 if rand.Intn(10)%2 == 0 {
 fill = &image.Uniform{color.White}
 }
 draw.Draw(img, image.Rect(x, y, x+10, y+10), fill, image.ZP, draw.Src)
 }
 }

 var Enc png.Encoder

 // set the best compression

 Enc.CompressionLevel = -3 //BestCompression

 // ok, write out the data into the new PNG file

 err = Enc.Encode(out, img)
 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 fmt.Println("Generated image to output.png \n")
 }

References :

http://golang.org/pkg/image/png/#Encoder

http://golang.org/pkg/image/png/#CompressionLevel

http://golang.org/pkg/image/png/#Encoder.Encode