mirror of
https://github.com/hajimehoshi/ebiten.git
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267 lines
9.1 KiB
HTML
267 lines
9.1 KiB
HTML
<!DOCTYPE html>
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<meta charset="utf-8">
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<meta property="og:image" itemprop="image primaryImageOfPage" content="https://hajimehoshi.github.io/ebiten/images/examples/piano.png">
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<meta name="description" content="Ebiten example - piano">
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<link rel="shortcut icon" href="../favicon.png" type="image/png" >
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<link rel="icon" href="../favicon.png" type="image/png" >
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<title>Ebiten example - piano</title>
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<link rel="stylesheet" href="../stylesheets/bootstrap.min.css">
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<link rel="stylesheet" href="../stylesheets/highlight-github.css">
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<link rel="stylesheet" href="../stylesheets/ebiten.css">
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<script src="../scripts/googleanalytics.js"></script>
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<nav class="navbar"><div class="container">
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<nav class="d-flex flex-row" style="width: 100%;">
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<div class="nav mr-auto"><a class="navbar-brand" href="../"><img src="../images/logo_white.svg" alt="EBITEN"></a></div>
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<ul class="nav">
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<li class="nav-item"><a class="nav-link" href="https://github.com/hajimehoshi/ebiten">GitHub</a></li>
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<li class="nav-item"><a class="nav-link" href="https://godoc.org/github.com/hajimehoshi/ebiten">GoDoc</a></li>
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<li class="nav-item"><a class="nav-link" href="https://github.com/hajimehoshi/ebiten/wiki">Wiki</a>
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<li class="nav-item"><a class="nav-link" href="https://ebiten-playground.github.io/">Playground</a>
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</ul>
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</nav>
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</div></nav>
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<main><div class="container">
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<h2>Ebiten example - piano</h2>
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<iframe src="piano.content.html" width="640" height="480"></iframe>
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<div class="card"><pre class="card-body"><code class="language-go">// +build example jsgo
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package main
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import (
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"fmt"
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"image/color"
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"log"
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"math"
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"github.com/golang/freetype/truetype"
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"golang.org/x/image/font"
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"github.com/hajimehoshi/ebiten"
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"github.com/hajimehoshi/ebiten/audio"
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"github.com/hajimehoshi/ebiten/ebitenutil"
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"github.com/hajimehoshi/ebiten/examples/resources/fonts"
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"github.com/hajimehoshi/ebiten/inpututil"
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"github.com/hajimehoshi/ebiten/text"
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)
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var (
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arcadeFont font.Face
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)
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func init() {
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tt, err := truetype.Parse(fonts.ArcadeN_ttf)
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if err != nil {
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log.Fatal(err)
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}
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const (
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arcadeFontSize = 8
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dpi = 72
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)
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arcadeFont = truetype.NewFace(tt, &truetype.Options{
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Size: arcadeFontSize,
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DPI: dpi,
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Hinting: font.HintingFull,
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})
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}
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const (
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screenWidth = 320
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screenHeight = 240
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sampleRate = 44100
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baseFreq = 220
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)
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var audioContext *audio.Context
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func init() {
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var err error
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audioContext, err = audio.NewContext(sampleRate)
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if err != nil {
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log.Fatal(err)
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}
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}
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// pianoAt returns an i-th sample of piano with the given frequency.
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func pianoAt(i int, freq float64) float64 {
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// Create piano-like waves with multiple sin waves.
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amp := []float64{1.0, 0.8, 0.6, 0.4, 0.2}
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x := []float64{4.0, 2.0, 1.0, 0.5, 0.25}
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v := 0.0
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for j := 0; j < len(amp); j++ {
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// Decay
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a := amp[j] * math.Exp(-5*float64(i)*freq/baseFreq/(x[j]*sampleRate))
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v += a * math.Sin(2.0*math.Pi*float64(i)*freq*float64(j+1)/sampleRate)
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}
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return v / 5.0
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}
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// toBytes returns the 2ch little endian 16bit byte sequence with the given left/right sequence.
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func toBytes(l, r []int16) []byte {
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if len(l) != len(r) {
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panic("len(l) must equal to len(r)")
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}
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b := make([]byte, len(l)*4)
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for i := range l {
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b[4*i] = byte(l[i])
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b[4*i+1] = byte(l[i] >> 8)
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b[4*i+2] = byte(r[i])
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b[4*i+3] = byte(r[i] >> 8)
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}
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return b
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}
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var (
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pianoNoteSamples = map[int][]byte{}
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pianoNoteSamplesInited = false
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pianoNoteSamplesInitCh = make(chan struct{})
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)
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func init() {
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// Initialize piano data.
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// This takes a little long time (especially on browsers),
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// so run this asynchronously and notice the progress.
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go func() {
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// Create a reference data and use this for other frequency.
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const refFreq = 110
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length := 4 * sampleRate * baseFreq / refFreq
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refData := make([]int16, length)
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for i := 0; i < length; i++ {
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refData[i] = int16(pianoAt(i, refFreq) * math.MaxInt16)
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}
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for i := range keys {
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freq := baseFreq * math.Exp2(float64(i-1)/12.0)
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// Clculate the wave data for the freq.
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length := 4 * sampleRate * baseFreq / int(freq)
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l := make([]int16, length)
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r := make([]int16, length)
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for i := 0; i < length; i++ {
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idx := int(float64(i) * freq / refFreq)
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if len(refData) <= idx {
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break
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}
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l[i] = refData[idx]
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}
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copy(r, l)
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n := toBytes(l, r)
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pianoNoteSamples[int(freq)] = n
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}
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close(pianoNoteSamplesInitCh)
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}()
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}
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// playNote plays piano sound with the given frequency.
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func playNote(freq float64) {
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f := int(freq)
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p, _ := audio.NewPlayerFromBytes(audioContext, pianoNoteSamples[f])
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p.Play()
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}
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var (
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pianoImage *ebiten.Image
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)
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func init() {
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pianoImage, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterDefault)
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const (
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keyWidth = 24
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y = 48
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)
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whiteKeys := []string{"A", "S", "D", "F", "G", "H", "J", "K", "L"}
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for i, k := range whiteKeys {
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x := i*keyWidth + 36
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height := 112
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ebitenutil.DrawRect(pianoImage, float64(x), float64(y), float64(keyWidth-1), float64(height), color.White)
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text.Draw(pianoImage, k, arcadeFont, x+8, y+height-8, color.Black)
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}
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blackKeys := []string{"Q", "W", "", "R", "T", "", "U", "I", "O"}
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for i, k := range blackKeys {
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if k == "" {
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continue
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}
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x := i*keyWidth + 24
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height := 64
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ebitenutil.DrawRect(pianoImage, float64(x), float64(y), float64(keyWidth-1), float64(height), color.Black)
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text.Draw(pianoImage, k, arcadeFont, x+8, y+height-8, color.White)
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}
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}
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var (
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keys = []ebiten.Key{
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ebiten.KeyQ,
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ebiten.KeyA,
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ebiten.KeyW,
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ebiten.KeyS,
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ebiten.KeyD,
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ebiten.KeyR,
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ebiten.KeyF,
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ebiten.KeyT,
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ebiten.KeyG,
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ebiten.KeyH,
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ebiten.KeyU,
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ebiten.KeyJ,
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ebiten.KeyI,
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ebiten.KeyK,
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ebiten.KeyO,
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ebiten.KeyL,
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}
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)
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func update(screen *ebiten.Image) error {
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// The piano data is still being initialized.
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// Get the progress if available.
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if !pianoNoteSamplesInited {
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select {
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case <-pianoNoteSamplesInitCh:
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pianoNoteSamplesInited = true
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default:
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}
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}
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if pianoNoteSamplesInited {
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for i, key := range keys {
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if !inpututil.IsKeyJustPressed(key) {
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continue
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}
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playNote(baseFreq * math.Exp2(float64(i-1)/12.0))
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}
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}
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if ebiten.IsRunningSlowly() {
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return nil
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}
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screen.Fill(color.RGBA{0x80, 0x80, 0xc0, 0xff})
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screen.DrawImage(pianoImage, nil)
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ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f", ebiten.CurrentFPS()))
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return nil
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}
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func main() {
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if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Piano (Ebiten Demo)"); err != nil {
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log.Fatal(err)
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}
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}
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</code></pre></div>
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</div></main>
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<footer><div class="container">
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<p>© 2013 Hajime Hoshi</p>
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<p>Code is licensed under <a href="https://github.com/hajimehoshi/ebiten/blob/master/LICENSE">the Apache License 2.0</a>.</p>
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<p>The content of this page is licensed under <a href="https://creativecommons.org/licenses/by/4.0/">the Creative Commons Attribution 4.0 License</a>.</p>
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</div></footer>
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<script src="../scripts/highlight.pack.js"></script>
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<script>hljs.initHighlightingOnLoad();</script>
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