Golang : Save image to PNG, JPEG or GIF format.
This tutorial will demonstrate how to save images into files. We will learn how to generate some random images and save the content from memory into PNG, JPG and GIF file. Basically, the codes are almost the same except for the slight variants to demonstrate how to use the Encode
functions.
JPG :
package main
import (
"flag"
"fmt"
"image"
"image/color"
"image/draw"
"image/jpeg"
"math/rand"
"os"
"time"
)
func main() {
flag.Parse()
rand.Seed(time.Now().UTC().UnixNano())
out, err := os.Create("./output.jpg")
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 opt jpeg.Options
opt.Quality = 80
// ok, write out the data into the new JPEG file
err = jpeg.Encode(out, img, &opt) // put quality to 80%
if err != nil {
fmt.Println(err)
os.Exit(1)
}
fmt.Println("Generated image to output.jpg \n")
}
PNG :
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)
}
}
// ok, write out the data into the new PNG file
err = png.Encode(out, img)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
fmt.Println("Generated image to output.png \n")
}
GIF :
package main
import (
"flag"
"fmt"
"image"
"image/color"
"image/draw"
"image/gif"
"math/rand"
"os"
"time"
)
func main() {
flag.Parse()
rand.Seed(time.Now().UTC().UnixNano())
out, err := os.Create("./output.gif")
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 opt gif.Options
opt.NumColors = 256 // you can add more parameters if you want
// ok, write out the data into the new GIF file
err = gif.Encode(out, img, &opt) // put num of colors to 256
if err != nil {
fmt.Println(err)
os.Exit(1)
}
fmt.Println("Generated image to output.gif \n")
}
Hope this simple tutorial will be able to assist you in dealing with popular image file formats.
See also : Golang : How to read JPG(JPEG), GIF and PNG files ?
By Adam Ng
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