/
server4.go
70 lines (59 loc) · 1.58 KB
/
server4.go
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// Generates GIF animations of random Lissajous figures. via a browser. It accepts cycles as a query parameter
package main
import (
"log"
"net/http"
"image"
"image/color"
"image/gif"
"io"
"math"
"math/rand"
"strconv"
"fmt"
)
var palette = []color.Color{color.White, color.Black}
const (
whiteIndex = 0 // first color in palette
blackIndex = 1 // next color in palette
)
func main() {
http.HandleFunc("/", handler)
log.Fatal(http.ListenAndServe("localhost:8000", nil))
}
func handler(w http.ResponseWriter, r *http.Request) {
cycles, ok := r.URL.Query()["cycles"]
cyc := 5
if (ok) {
c, err := strconv.Atoi(cycles[0])
if err != nil {
fmt.Printf("errr %s", err)
}
cyc = c
}
lissajous(w, cyc)
}
func lissajous(out io.Writer, cycles int) {
const(
res = 0.001 // angular resolution
size = 1000 // image canvas convers [-size..+size]
nframes = 64 // number of animation frames
delay = 8 // delay between frames in 10ms units
)
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),blackIndex)
}
phase += 0.1
anim.Delay = append(anim.Delay, delay)
anim.Image = append(anim.Image, img)
}
gif.EncodeAll(out, &anim) // NOTE: ignoring encoding errors
}