105 lines
2.3 KiB
Go
105 lines
2.3 KiB
Go
package main
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import (
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"fmt"
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"image"
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"image/color"
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"image/draw"
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"image/gif"
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"log"
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"math"
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"math/rand"
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"os"
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"time"
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)
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var bwPalette = color.Palette{
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color.Transparent,
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color.White,
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color.RGBA{R: 0xff, A: 0xff},
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color.RGBA{G: 0xff, A: 0xff},
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color.RGBA{B: 0xff, A: 0xff},
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}
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func main() {
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const (
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width = 160
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frames = 100
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pointsPerFrame = 50
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delay = 100 * time.Millisecond
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filename = "chaos_anim.gif"
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)
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var tan60 = math.Sin(math.Pi / 3)
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height := int(math.Round(float64(width) * tan60))
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b := image.Rect(0, 0, width, height)
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vertices := [...]image.Point{
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{0, height}, {width, height}, {width / 2, 0},
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}
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// Make a filled triangle.
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m := image.NewPaletted(b, bwPalette)
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for y := b.Min.Y; y < b.Max.Y; y++ {
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bg := int(math.Round(float64(b.Max.Y-y) / 2 / tan60))
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for x := b.Min.X + bg; x < b.Max.X-bg; x++ {
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m.SetColorIndex(x, y, 1)
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}
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}
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// Pick starting point
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var p image.Point
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rand.Seed(time.Now().UnixNano())
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p.Y = rand.Intn(height) + b.Min.Y
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p.X = rand.Intn(width) + b.Min.X // TODO: make within triangle
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anim := newAnim(frames, delay)
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addFrame(anim, m)
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for i := 1; i < frames; i++ {
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for j := 0; j < pointsPerFrame; j++ {
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// Pick a random vertex
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vi := rand.Intn(len(vertices))
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v := vertices[vi]
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// Move p halfway there
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p.X = (p.X + v.X) / 2
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p.Y = (p.Y + v.Y) / 2
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m.SetColorIndex(p.X, p.Y, uint8(2+vi))
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}
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addFrame(anim, m)
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}
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if err := writeAnim(anim, filename); err != nil {
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log.Fatal(err)
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}
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fmt.Printf("wrote to %q\n", filename)
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}
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// Stuff for making a simple GIF animation.
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func newAnim(frames int, delay time.Duration) *gif.GIF {
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const gifDelayScale = 10 * time.Millisecond
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g := &gif.GIF{
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Image: make([]*image.Paletted, 0, frames),
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Delay: make([]int, 1, frames),
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}
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g.Delay[0] = int(delay / gifDelayScale)
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return g
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}
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func addFrame(anim *gif.GIF, m *image.Paletted) {
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b := m.Bounds()
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dst := image.NewPaletted(b, m.Palette)
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draw.Draw(dst, b, m, image.ZP, draw.Src)
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anim.Image = append(anim.Image, dst)
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if len(anim.Delay) < len(anim.Image) {
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anim.Delay = append(anim.Delay, anim.Delay[0])
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}
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}
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func writeAnim(anim *gif.GIF, filename string) error {
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f, err := os.Create(filename)
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if err != nil {
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return err
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}
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err = gif.EncodeAll(f, anim)
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if cerr := f.Close(); err == nil {
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err = cerr
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}
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return err
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}
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