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lissajous.go
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/
lissajous.go
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// Lissajous generates GIF animations of random Lissajous figures
package main
import (
"image"
"image/color"
"image/gif"
"io"
"log"
"math"
"math/rand"
"net/http"
"strconv"
)
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 (
whiteIndex = 0 // first color in palette
blackIndex = 1 // next color in palette
)
func main() {
http.HandleFunc("/lissajous", func(w http.ResponseWriter, r *http.Request) {
log.Printf("%s %s %s\n", r.Method, r.URL, r.Proto)
log.Printf("Host = %q\n", r.Host)
log.Printf("RemoteAddr = %q\n", r.RemoteAddr)
if err := r.ParseForm(); err != nil {
log.Print(err)
}
for k, v := range r.Form {
log.Printf("Form[%q] = %q\n", k, v)
}
cycles, _ := strconv.Atoi(r.Form["cycles"][0])
log.Printf("lissajous(%d)", cycles)
lissajous(w, cycles)
})
log.Print("Listening and Serving")
log.Fatal(http.ListenAndServe("localhost:8000", nil))
}
// cycles = 5 // number of complete x oscillator revolutions
func lissajous(out io.Writer, cycles int) {
const (
res = 0.001 // angular resolution
size = 100 // image canvas covers [-size..+size]
nframes = 64 // number of animation frames
delay = 8 // delay between frames in 10ms units
)
cycles = 5
freq := rand.Float64() * 3.0 // relative frequency of y oscillator
anim := gif.GIF{LoopCount: nframes}
phase := 0.0 // phase difference
for i := 0; i < nframes; i++ {
rect := image.Rect(0, 0, 2*size+1, 2*size+1)
img := image.NewPaletted(rect, palette)
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*size+0.5), size+int(y*size+0.5), (1 + (nframes % 3)))
}
phase += 0.1
anim.Delay = append(anim.Delay, delay)
anim.Image = append(anim.Image, img)
}
gif.EncodeAll(out, &anim) // NOTE: ignoring encoding errors
}