Ebiten example - font

// +build example

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 func() {
                _ = 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,
                }),
        }
        y := size
        for _, s := range text {
                d.Dot = fixed.P(0, y)
                d.DrawString(s)
                y += size
        }
        textImage.ReplacePixels(dst.Pix)
        return nil
}

func update(screen *ebiten.Image) error {
        screen.DrawImage(textImage, &ebiten.DrawImageOptions{})
        return nil
}

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