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.
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//go:build example
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// +build example
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package main
import (
"fmt"
"image/color"
"log"
"math"
"golang.org/x/image/font"
"golang.org/x/image/font/opentype"
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"github.com/hajimehoshi/ebiten/v2"
"github.com/hajimehoshi/ebiten/v2/audio"
"github.com/hajimehoshi/ebiten/v2/ebitenutil"
"github.com/hajimehoshi/ebiten/v2/examples/resources/fonts"
"github.com/hajimehoshi/ebiten/v2/inpututil"
"github.com/hajimehoshi/ebiten/v2/text"
)
var (
arcadeFont font.Face
)
func init() {
tt, err := opentype.Parse(fonts.PressStart2P_ttf)
if err != nil {
log.Fatal(err)
}
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const (
arcadeFontSize = 8
dpi = 72
)
arcadeFont, err = opentype.NewFace(tt, &opentype.FaceOptions{
Size: arcadeFontSize,
DPI: dpi,
Hinting: font.HintingFull,
})
if err != nil {
log.Fatal(err)
}
}
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const (
screenWidth = 320
screenHeight = 240
sampleRate = 48000
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baseFreq = 220
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)
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// pianoAt returns an i-th sample of piano with the given frequency.
func pianoAt(i int, freq float64) float64 {
// Create piano-like waves with multiple sin waves.
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amp := []float64{1.0, 0.8, 0.6, 0.4, 0.2}
x := []float64{4.0, 2.0, 1.0, 0.5, 0.25}
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v := 0.0
for j := 0; j < len(amp); j++ {
// Decay
a := amp[j] * math.Exp(-5*float64(i)*freq/baseFreq/(x[j]*sampleRate))
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.
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
}
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var (
pianoNoteSamples = map[int][]byte{}
pianoNoteSamplesInited = false
pianoNoteSamplesInitCh = make(chan struct{})
)
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func init() {
// Initialize piano data.
// This takes a little long time (especially on browsers),
// so run this asynchronously and notice the progress.
go func() {
// Create a reference data and use this for other frequency.
const refFreq = 110
length := 4 * sampleRate * baseFreq / refFreq
refData := make([]int16, length)
for i := 0; i < length; i++ {
refData[i] = int16(pianoAt(i, refFreq) * math.MaxInt16)
}
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for i := range keys {
freq := baseFreq * math.Exp2(float64(i-1)/12.0)
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// Clculate the wave data for the freq.
length := 4 * sampleRate * baseFreq / int(freq)
l := make([]int16, length)
r := make([]int16, length)
for i := 0; i < length; i++ {
idx := int(float64(i) * freq / refFreq)
if len(refData) <= idx {
break
}
l[i] = refData[idx]
}
copy(r, l)
n := toBytes(l, r)
pianoNoteSamples[int(freq)] = n
}
close(pianoNoteSamplesInitCh)
}()
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}
var (
pianoImage = ebiten.NewImage(screenWidth, screenHeight)
)
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func init() {
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const (
keyWidth = 24
y = 48
)
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whiteKeys := []string{"A", "S", "D", "F", "G", "H", "J", "K", "L"}
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)
text.Draw(pianoImage, k, arcadeFont, x+8, y+height-8, color.Black)
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}
blackKeys := []string{"Q", "W", "", "R", "T", "", "U", "I", "O"}
for i, k := range blackKeys {
if k == "" {
continue
}
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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)
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 (
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,
}
)
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type Game struct {
audioContext *audio.Context
}
func NewGame() *Game {
return &Game{
audioContext: audio.NewContext(sampleRate),
}
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}
func (g *Game) Update() error {
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// The piano data is still being initialized.
// Get the progress if available.
if !pianoNoteSamplesInited {
select {
case <-pianoNoteSamplesInitCh:
pianoNoteSamplesInited = true
default:
}
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}
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if pianoNoteSamplesInited {
for i, key := range keys {
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if !inpututil.IsKeyJustPressed(key) {
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continue
}
g.playNote(baseFreq * math.Exp2(float64(i-1)/12.0))
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}
}
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return nil
}
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// playNote plays piano sound with the given frequency.
func (g *Game) playNote(freq float64) {
f := int(freq)
p := g.audioContext.NewPlayerFromBytes(pianoNoteSamples[f])
p.Play()
}
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func (g *Game) Draw(screen *ebiten.Image) {
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("TPS: %0.2f", ebiten.ActualTPS()))
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}
func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
return screenWidth, screenHeight
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}
func main() {
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ebiten.SetWindowSize(screenWidth*2, screenHeight*2)
ebiten.SetWindowTitle("Piano (Ebiten Demo)")
if err := ebiten.RunGame(NewGame()); err != nil {
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log.Fatal(err)
}
}