ebiten/examples/noise/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
package main
import (
"fmt"
"image"
"log"
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"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/ebitenutil"
)
const (
screenWidth = 320
screenHeight = 240
)
var (
noiseImage *image.RGBA
)
type rand struct {
x, y, z, w uint32
}
func (r *rand) next() uint32 {
// math/rand is too slow to keep 60 FPS on web browsers.
// Use Xorshift instead: http://en.wikipedia.org/wiki/Xorshift
t := r.x ^ (r.x << 11)
r.x, r.y, r.z = r.y, r.z, r.w
r.w = (r.w ^ (r.w >> 19)) ^ (t ^ (t >> 8))
return r.w
}
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var theRand = &rand{12345678, 4185243, 776511, 45411}
func update(screen *ebiten.Image) error {
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// Generate the noise with random RGB values.
const l = screenWidth * screenHeight
for i := 0; i < l; i++ {
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x := theRand.next()
noiseImage.Pix[4*i] = uint8(x >> 24)
noiseImage.Pix[4*i+1] = uint8(x >> 16)
noiseImage.Pix[4*i+2] = uint8(x >> 8)
noiseImage.Pix[4*i+3] = 0xff
}
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if ebiten.IsRunningSlowly() {
return nil
}
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screen.ReplacePixels(noiseImage.Pix)
ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %f", ebiten.CurrentFPS()))
return nil
}
func main() {
noiseImage = image.NewRGBA(image.Rect(0, 0, screenWidth, screenHeight))
if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Noise (Ebiten Demo)"); err != nil {
log.Fatal(err)
}
}