ebiten/examples/piano/main.go

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// Copyright 2015 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// +build example
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package main
import (
"fmt"
"image/color"
"log"
"math"
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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/common"
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)
const (
screenWidth = 320
screenHeight = 240
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sampleRate = 44100
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)
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var audioContext *audio.Context
func init() {
var err error
audioContext, err = audio.NewContext(sampleRate)
if err != nil {
log.Fatal(err)
}
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}
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var pcm = make([]float64, 4*sampleRate)
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const baseFreq = 220
func init() {
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
for j := 0; j < len(amp); j++ {
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a := amp[j] * math.Exp(-5*float64(i)/(x[j]*sampleRate))
v += a * math.Sin(2.0*math.Pi*float64(i)*baseFreq*float64(j+1)/sampleRate)
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}
pcm[i] = v / 5.0
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}
}
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var (
noteCache = map[int][]byte{}
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)
func toBytes(l, r []int16) []byte {
if len(l) != len(r) {
panic("len(l) must equal to len(r)")
}
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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])
b[4*i+1] = byte(l[i] >> 8)
b[4*i+2] = byte(r[i])
b[4*i+3] = byte(r[i] >> 8)
}
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return b
}
func addNote(freq float64, vol float64) {
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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 {
p, _ := audio.NewPlayerFromBytes(audioContext, n)
p.Play()
return
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}
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length := len(pcm) * baseFreq / f
l := make([]int16, length)
r := make([]int16, length)
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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
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}
n := toBytes(l, r)
noteCache[f] = n
p, _ := audio.NewPlayerFromBytes(audioContext, n)
p.Play()
return
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}
var keys = []ebiten.Key{
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ebiten.KeyQ,
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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
)
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func init() {
imagePiano, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterNearest)
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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
ebitenutil.DrawRect(imagePiano, float64(x), float64(y), float64(width-1), float64(height), color.White)
common.ArcadeFont.DrawText(imagePiano, k, x+8, y+height-16, 1, color.Black)
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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
ebitenutil.DrawRect(imagePiano, float64(x), float64(y), float64(width-1), float64(height), color.Black)
common.ArcadeFont.DrawText(imagePiano, k, x+8, y+height-16, 1, color.White)
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}
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}
func update(screen *ebiten.Image) error {
updateInput()
for i, key := range keys {
if keyStates[key] != 1 {
continue
}
addNote(220*math.Exp2(float64(i-1)/12.0), 1.0)
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}
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if ebiten.IsRunningSlowly() {
return nil
}
screen.Fill(color.RGBA{0x80, 0x80, 0xc0, 0xff})
screen.DrawImage(imagePiano, nil)
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ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f", ebiten.CurrentFPS()))
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return nil
}
func main() {
if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Piano (Ebiten Demo)"); err != nil {
log.Fatal(err)
}
}