ebiten/examples/mandelbrot/main.go
2018-02-14 03:00:00 +09:00

98 lines
2.2 KiB
Go

// Copyright 2017 The Ebiten Authors
//
// 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 (
"log"
"math"
"github.com/hajimehoshi/ebiten"
)
const (
screenWidth = 640
screenHeight = 640
maxIt = 128
)
var (
offscreen *ebiten.Image
offscreenPix []byte
palette [maxIt]byte
)
func init() {
offscreen, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterDefault)
offscreenPix = make([]byte, screenWidth*screenHeight*4)
for i := range palette {
palette[i] = byte(math.Sqrt(float64(i)/float64(len(palette))) * 0x80)
}
}
func color(it int) (r, g, b byte) {
if it == maxIt {
return 0xff, 0xff, 0xff
}
c := palette[it]
return c, c, c
}
func updateOffscreen(centerX, centerY, size float64) {
for j := 0; j < screenHeight; j++ {
for i := 0; i < screenHeight; i++ {
x := float64(i)*size/screenWidth - size/2 + centerX
y := (screenHeight-float64(j))*size/screenHeight - size/2 + centerY
c := complex(x, y)
z := complex(0, 0)
it := 0
for ; it < maxIt; it++ {
z = z*z + c
if real(z)*real(z)+imag(z)*imag(z) > 4 {
break
}
}
r, g, b := color(it)
p := 4 * (i + j*screenWidth)
offscreenPix[p] = r
offscreenPix[p+1] = g
offscreenPix[p+2] = b
offscreenPix[p+3] = 0xff
}
}
offscreen.ReplacePixels(offscreenPix)
}
func init() {
// Now it is not feasible to call updateOffscreen every frame due to performance.
updateOffscreen(-0.75, 0.25, 2)
}
func update(screen *ebiten.Image) error {
if ebiten.IsRunningSlowly() {
return nil
}
screen.DrawImage(offscreen, nil)
return nil
}
func main() {
if err := ebiten.Run(update, screenWidth, screenHeight, 1, "Mandelbrot (Ebiten Demo)"); err != nil {
log.Fatal(err)
}
}