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<!DOCTYPE html>
< link rel = "shortcut icon" href = "../favicon.png" type = "image/png" >
< link rel = "icon" href = "../favicon.png" type = "image/png" >
< title > Ebiten example - piano< / title >
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< link rel = "stylesheet" href = "/stylesheets/bootstrap.min.css" >
< link rel = "stylesheet" href = "/stylesheets/ebiten.css" >
< header class = "navbar" > < div class = "container" >
< div class = "navbar-header" >
< a class = "navbar-brand" href = "/" > Ebiten< / a >
< / div >
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< nav class = "collapse navbar-collapse" >
< ul class = "nav navbar-nav navbar-right" >
< li > < a href = "https://github.com/hajimehoshi/ebiten" > GitHub< / a > < / li >
< li > < a href = "http://godoc.org/github.com/hajimehoshi/ebiten" > GoDoc< / a > < / li >
< li > < a href = "https://github.com/hajimehoshi/ebiten/wiki" > Wiki< / a >
< / ul >
< / nav >
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< / header >
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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 >
< pre > < code > // + build example
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package main
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import (
" fmt"
" image/color"
" log"
" math"
" github.com/hajimehoshi/ebiten"
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" github.com/hajimehoshi/ebiten/audio"
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" github.com/hajimehoshi/ebiten/ebitenutil"
" github.com/hajimehoshi/ebiten/examples/common"
)
const (
screenWidth = 320
screenHeight = 240
sampleRate = 44100
)
var audioContext *audio.Context
func init() {
var err error
audioContext, err = audio.NewContext(sampleRate)
if err != nil {
log.Fatal(err)
}
}
var pcm = make([]float64, 4*sampleRate)
const baseFreq = 220
func init() {
s := float64(sampleRate)
amp := []float64{1.0, 0.8, 0.6, 0.4, 0.2}
x := []float64{4.0, 2.0, 1.0, 0.5, 0.25}
for i := 0; i < len(pcm); i+ + {
v := 0.0
twoPiF := 2.0 * math.Pi * baseFreq
for j := 0; j < len(amp); j+ + {
a := amp[j] * math.Exp(-5*float64(i)/(x[j]*s))
v + = a * math.Sin(float64(i)*twoPiF*float64(j+ 1)/s)
}
pcm[i] = v / 5.0
}
}
var (
noteCache = map[int][]byte{}
)
func toBytes(l, r []int16) []byte {
if len(l) != len(r) {
panic(" len(l) must equal to len(r)" )
}
b := make([]byte, len(l)*4)
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for i := range l {
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b[4*i] = byte(l[i])
b[4*i+ 1] = byte(l[i] > > 8)
b[4*i+ 2] = byte(r[i])
b[4*i+ 3] = byte(r[i] > > 8)
}
return b
}
func addNote(freq float64, vol float64) error {
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// TODO: Call Close method of *audio.Player.
// However, this works without Close because Close is automatically called when GC
// collects a *audio.Player object.
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f := int(freq)
if n, ok := noteCache[f]; ok {
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p, err := audio.NewPlayerFromBytes(audioContext, n)
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if err != nil {
return err
}
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if err := p.Play(); err != nil {
return err
}
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return nil
}
length := len(pcm) * baseFreq / f
l := make([]int16, length)
r := make([]int16, length)
j := 0
jj := 0
for i := 0; i < len(l); i+ + {
p := pcm[j]
l[i] = int16(p * vol * math.MaxInt16)
r[i] = l[i]
jj + = f
j = jj / baseFreq
}
n := toBytes(l, r)
noteCache[f] = n
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p, err := audio.NewPlayerFromBytes(audioContext, n)
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if err != nil {
return err
}
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if err := p.Play(); err != nil {
return err
}
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return nil
}
var keys = []ebiten.Key{
ebiten.KeyQ,
ebiten.KeyA,
ebiten.KeyW,
ebiten.KeyS,
ebiten.KeyD,
ebiten.KeyR,
ebiten.KeyF,
ebiten.KeyT,
ebiten.KeyG,
ebiten.KeyH,
ebiten.KeyU,
ebiten.KeyJ,
ebiten.KeyI,
ebiten.KeyK,
ebiten.KeyO,
ebiten.KeyL,
}
var keyStates = map[ebiten.Key]int{}
func init() {
for _, key := range keys {
keyStates[key] = 0
}
}
func updateInput() {
for _, key := range keys {
if !ebiten.IsKeyPressed(key) {
keyStates[key] = 0
continue
}
keyStates[key]+ +
}
}
var (
imagePiano *ebiten.Image
)
func init() {
var err error
imageEmpty, err := ebiten.NewImage(16, 16, ebiten.FilterNearest)
if err != nil {
panic(err)
}
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if err := imageEmpty.Fill(color.White); err != nil {
panic(err)
}
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imagePiano, err = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterNearest)
if err != nil {
panic(err)
}
whiteKeys := []string{" A" , " S" , " D" , " F" , " G" , " H" , " J" , " K" , " L" }
width := 24
y := 48
for i, k := range whiteKeys {
x := i*width + 36
height := 112
op := & ebiten.DrawImageOptions{}
w, h := imageEmpty.Size()
op.GeoM.Scale(float64(width-1)/float64(w), float64(height)/float64(h))
op.GeoM.Translate(float64(x), float64(y))
op.ColorM.Scale(1, 1, 1, 1)
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if err := imagePiano.DrawImage(imageEmpty, op); err != nil {
panic(err)
}
if err := common.ArcadeFont.DrawText(imagePiano, k, x+ 8, y+ height-16, 1, color.Black); err != nil {
panic(err)
}
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}
blackKeys := []string{" Q" , " W" , " " , " R" , " T" , " " , " U" , " I" , " O" }
for i, k := range blackKeys {
if k == " " {
continue
}
x := i*width + 24
height := 64
op := & ebiten.DrawImageOptions{}
w, h := imageEmpty.Size()
op.GeoM.Scale(float64(width-1)/float64(w), float64(height)/float64(h))
op.GeoM.Translate(float64(x), float64(y))
op.ColorM.Scale(0, 0, 0, 1)
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if err := imagePiano.DrawImage(imageEmpty, op); err != nil {
panic(err)
}
if err := common.ArcadeFont.DrawText(imagePiano, k, x+ 8, y+ height-16, 1, color.White); err != nil {
panic(err)
}
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}
}
func update(screen *ebiten.Image) error {
updateInput()
for i, key := range keys {
if keyStates[key] != 1 {
continue
}
if err := addNote(220*math.Exp2(float64(i-1)/12.0), 1.0); err != nil {
return err
}
}
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if err := screen.Fill(color.RGBA{0x80, 0x80, 0xc0, 0xff}); err != nil {
return err
}
if err := screen.DrawImage(imagePiano, nil); err != nil {
return err
}
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if err := ebitenutil.DebugPrint(screen, fmt.Sprintf(" FPS: %0.2f" , ebiten.CurrentFPS())); err != nil {
return err
}
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if err := audioContext.Update(); err != nil {
return err
}
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return nil
}
func main() {
if err := ebiten.Run(update, screenWidth, screenHeight, 2, " Piano (Ebiten Demo)" ); err != nil {
log.Fatal(err)
}
}
< / code > < / pre >
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< / div > < / main >
< footer > < div class = "container" >
< p > © 2013 Hajime Hoshi< / p >
< p > Code is licensed under < a href = "https://github.com/hajimehoshi/ebiten/blob/master/LICENSE" > Apache License 2.0< / a > .< / p >
< 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 >
< / div > < / footer >
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