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package main
import (
"image"
"image/color"
"image/gif"
"io"
"math"
"math/rand/v2"
"os"
)
var palette = []color.Color{
color.Black,
color.RGBA{0x00, 0xff, 0x00, 0xff},
color.RGBA{0xff, 0x00, 0x00, 0xff},
color.RGBA{0x00, 0x00, 0xff, 0xff},
}
const (
backgroundIndex = iota
foregroundIndex
)
func main() {
lissajous(os.Stdout)
}
func lissajous(out io.Writer) {
const (
cycles = 5
res = 0.001
size = 100
nframes = 64
delay = 8
)
// Note that this generates the exact same random number per
// run of the program.
freq := rand.Float64() * 3.0
anim := gif.GIF{LoopCount: nframes}
for i := range nframes {
img := newImage(size, cycles, float64(i)/10, res, freq)
anim.Delay = append(anim.Delay, delay)
anim.Image = append(anim.Image, img)
}
gif.EncodeAll(out, &anim)
}
func newImage(size, cycles int, phase, res, freq float64) *image.Paletted {
rect := image.Rect(0, 0, 2*size+1, 2*size+1)
img := image.NewPaletted(rect, palette)
randIndex := 1 + uint8(rand.IntN(len(palette)-1))
for t := 0.0; t < float64(cycles)*2*math.Pi; t += res {
x := math.Sin(t)
y := math.Sin(t*freq + phase)
img.SetColorIndex(size+int(x*float64(size)+0.5), size+int(y*float64(size)+0.5), randIndex)
}
return img
}
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