Add example/piano

example/piano/main.go

@@ -0,0 +1,125 @@
+// 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.
+
+package main
+
+import (
+	"fmt"
+	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
+	"github.com/hajimehoshi/ebiten/exp/audio"
+	"log"
+	"math"
+)
+
+const (
+	screenWidth  = 320
+	screenHeight = 240
+)
+
+var pcm = make([]float64, 4*audio.SampleRate())
+
+const baseFreq = 220
+
+func init() {
+	s := float64(audio.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
+	}
+}
+
+func addNote(freq float64, vol float64) {
+	f := int(freq)
+	length := len(pcm) * baseFreq / f
+	l := make([]int16, length)
+	r := make([]int16, length)
+	if baseFreq <= freq {
+		x := 0
+		i := 0
+		for _, p := range pcm {
+			x += baseFreq
+			x %= f
+			if x < baseFreq {
+				l[i] = int16(p * vol * math.MaxInt16)
+				r[i] = l[i]
+				i++
+			}
+		}
+	} else {
+		// Not implemented
+	}
+	audio.Play(-1, l, r)
+}
+
+var keys = []ebiten.Key{
+	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]++
+	}
+}
+
+func update(screen *ebiten.Image) error {
+	updateInput()
+	for i, key := range keys {
+		if keyStates[key] != 1 {
+			continue
+		}
+		addNote(220*math.Exp2(float64(i)/12.0), 1.0/8.0)
+	}
+	ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f", ebiten.CurrentFPS()))
+	return nil
+}
+
+func main() {
+	if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Piano (Ebiten Demo)"); err != nil {
+		log.Fatal(err)
+	}
+}