How to Process Images in Go (image Package)

Use the image package to decode image files and the image/draw package to manipulate pixels. The following example loads a PNG file, creates a new image, and draws a red rectangle on it.

package main

import (
	"image"
	"image/color"
	"image/draw"
	"image/png"
	"os"
)

func main() {
	f, _ := os.Open("input.png")
	orig, _, _ := png.Decode(f)
	f.Close()

	newImg := image.NewRGBA(orig.Bounds())
	rect := image.Rect(10, 10, 100, 100)
	c := color.RGBA{255, 0, 0, 255}
	draw.Draw(newImg, rect, image.NewUniform(c), image.Point{}, draw.Src)

	out, _ := os.Create("output.png")
	png.Encode(out, newImg)
	out.Close()
}

The Go image package lets you read, create, and modify pictures in your code. Think of it like a digital canvas where you can load an existing photo and paint new shapes or colors on top of it. You use it whenever you need to generate thumbnails, add watermarks, or process images programmatically.