package main

import (
	"fmt"
	"image"
	"image/draw"
	"image/jpeg"
	"os"
)

func main() {
	imgFile1, err := os.Open("img1.jpg")
	if err != nil {
		fmt.Println(err)
	}
	imgFile2, err := os.Open("img2.jpg")
	if err != nil {
		fmt.Println(err)
	}
	img1, _, err := image.Decode(imgFile1)
	if err != nil {
		fmt.Println(err)
	}
	img2, _, err := image.Decode(imgFile2)
	if err != nil {
		fmt.Println(err)
	}

	//starting position of the second image (bottom left)
	sp2 := image.Point{img1.Bounds().Dx(), 0}
	//new rectangle for the second image
	r2 := image.Rectangle{sp2, sp2.Add(img2.Bounds().Size())}
	//rectangle for the big image
	r := image.Rectangle{image.Point{0, 0}, r2.Max}
	rgba := image.NewRGBA(r)

	draw.Draw(rgba, img1.Bounds(), img1, image.Point{0, 0}, draw.Src)
	draw.Draw(rgba, r2, img2, image.Point{0, 0}, draw.Src)

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

	var opt jpeg.Options
	opt.Quality = 80

	jpeg.Encode(out, rgba, &opt)
}