Ebiten example - font

package main

import (
    "image"
    "io/ioutil"
    "log"

    "github.com/golang/freetype/truetype"
    "github.com/hajimehoshi/ebiten"
    "github.com/hajimehoshi/ebiten/ebitenutil"
    "golang.org/x/image/font"
    "golang.org/x/image/math/fixed"
)

const (
    screenWidth  = 640
    screenHeight = 480
)

var (
    textImage *ebiten.Image
)

var text = []string{
    "The quick brown fox jumps over the lazy dog.",
    "",
    // A head part of a Japanese novel 山月記 (Sangetsuki)
    // See http://www.aozora.gr.jp/cards/000119/files/624_14544.html.
    "隴西の李徴は博学才穎、天宝の末年、",
    "若くして名を虎榜に連ね、",
    "ついで江南尉に補せられたが、",
    "性、狷介、自ら恃むところ頗厚く、",
    "賤吏に甘んずるを潔しとしなかった。",
}

func parseFont() error {
    f, err := ebitenutil.OpenFile("_resources/fonts/mplus-1p-regular.ttf")
    if err != nil {
        return err
    }
    defer f.Close()
    b, err := ioutil.ReadAll(f)
    if err != nil {
        return err
    }
    tt, err := truetype.Parse(b)
    if err != nil {
        return err
    }
    w, h := textImage.Size()
    dst := image.NewRGBA(image.Rect(0, 0, w, h))
    const size = 24
    const dpi = 72
    d := &font.Drawer{
        Dst: dst,
        Src: image.White,
        Face: truetype.NewFace(tt, &truetype.Options{
            Size:    size,
            DPI:     dpi,
            Hinting: font.HintingFull,
        }),
    }
    dy := size * dpi / 72
    y := dy
    for _, s := range text {
        d.Dot = fixed.P(0, y)
        d.DrawString(s)
        y += dy
    }
    return textImage.ReplacePixels(dst.Pix)
}

func update(screen *ebiten.Image) error {
    if err := screen.DrawImage(textImage, &ebiten.DrawImageOptions{}); err != nil {
        return err
    }
    return nil
}

func main() {
    var err error
    textImage, err = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterNearest)
    if err != nil {
        log.Fatal(err)
    }
    if err := parseFont(); err != nil {
        log.Fatal(err)
    }
    if err := ebiten.Run(update, screenWidth, screenHeight, 1, "Font (Ebiten Demo)"); err != nil {
        log.Fatal(err)
    }
}