test.go

package main

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

	"github.com/pkg/browser"
	"golang.org/x/image/font"
	"golang.org/x/image/font/opentype"
	"golang.org/x/image/font/sfnt"
	"golang.org/x/image/math/fixed"
)

func run() error {
	width := 640

	text := `All human beings are born free and equal in dignity and rights.`

	const (
		offsetX = 8
		offsetY = 8
	)

	const (
		size = 72
		dotX = 4
		dotY = 12
		glyphWidth = size
		glyphHeight = size * 1.5
	)

	height := glyphHeight*len(strings.Split(strings.TrimSpace(text), "\n")) + offsetX*2
	dst := image.NewRGBA(image.Rect(0, 0, width, height))
	draw.Draw(dst, dst.Bounds(), image.NewUniform(color.White), image.ZP, draw.Src)

  // I used NotoSerifCJKjp-Regular.otf
	otf, err := os.Open("test.otf")
	if err != nil {
		return err
	}
	defer otf.Close()

	sf, err := sfnt.ParseReaderAt(otf)
	if err != nil {
		return err
	}

	f, err := opentype.NewFace(sf, &opentype.FaceOptions{
		Size: size,
		DPI: 72,
	})
	if err != nil {
		return err
	}

	d := font.Drawer{
		Dst:  dst,
		Src:  image.NewUniform(color.Black),
		Face: f,
		Dot:  fixed.P(dotX+offsetX, dotY+offsetY),
	}

	for _, l := range strings.Split(text, "\n") {
		d.DrawString(l)
		d.Dot.X = fixed.I(dotX + offsetX)
		d.Dot.Y += f.Metrics().Height
	}

	path := "example.png"
	fout, err := os.Create(path)
	if err != nil {
		return err
	}
	defer fout.Close()

	if err := png.Encode(fout, d.Dst); err != nil {
		return err
	}

	if err := browser.OpenFile(path); err != nil {
		return err
	}
	return nil
}

func main() {
	if err := run(); err != nil {
		panic(err)
	}
}