Draw text to image in Go

main.go

package main

import (
	"bufio"
	"fmt"
	"image"
	"image/color"
	"image/draw"
	"image/jpeg"
	"log"
	"os"

	"golang.org/x/image/font"
	"golang.org/x/image/font/opentype"
	"golang.org/x/image/math/fixed"

	_ "embed"
	_ "image/png"
)

var (
	//go:embed fonts/Aileron-Regular.otf
	fontBytes []byte
)

func main() {
	file, err := os.Open("source.png")
	if err != nil {
		log.Fatalf("failed to open file: %v", err)
	}
	defer file.Close()
	
	img, _, err := image.Decode(file)
	if err != nil {
		log.Fatalf("failed to decode image: %v", err)
	}
	
	dst := image.NewRGBA(img.Bounds())
	draw.Draw(dst, dst.Bounds(), img, image.Point{}, draw.Src)
	
	f, err := opentype.Parse(fontBytes)
	if err != nil {
		log.Fatalf("failed to parse font: %v", err)
	}
	face, err := opentype.NewFace(f, &opentype.FaceOptions{
		Size:    float64(img.Bounds().Dx() / 5),
		DPI:     72,
		Hinting: font.HintingNone,
	})
	if err != nil {
		log.Fatalf("failed to create new face: %v", err)
	}

	d := &font.Drawer{
		Dst:  dst,
		Src:  image.NewUniform(color.RGBA{255, 255, 255, 255}),
		Face: face,
		Dot:  fixed.Point26_6{fixed.Int26_6(img.Bounds().Dx() / 11 * 3 * 64), fixed.Int26_6(img.Bounds().Dy() / 5 * 3 * 64)},
	}
	d.DrawString("LGTM")
	
	newFile, err := os.Create("out.jpg")
	if err != nil {
		log.Fatalf("failed to create file: %v", err)
	}
	defer newFile.Close()

	b := bufio.NewWriter(newFile)
	if err := jpeg.Encode(b, dst, &jpeg.Options{Quality: 100}); err != nil {
		log.Fatalf("failed to encode image: %v", err)
	}
}