Data commit

Task/Polyspiral/Go/polyspiral.go

@@ -0,0 +1,113 @@
+package main
+
+import (
+    "image"
+    "image/color"
+    "image/gif"
+    "log"
+    "math"
+    "os"
+)
+
+func drawLine(img *image.Paletted, x1, y1, x2, y2 int, ci uint8) {
+    var first, last int
+    if x2 != x1 {
+        m := float64(y2-y1) / float64(x2-x1)
+        if x1 < x2 {
+            first, last = x1, x2
+        } else {
+            first, last = x2, x1
+        }
+        for x := first; x <= last; x++ {
+            y := int(m*float64(x-x1)+0.5) + y1
+            img.SetColorIndex(x, y, ci)
+        }
+    } else {
+        if y1 < y2 {
+            first, last = y1, y2
+        } else {
+            first, last = y2, y1
+        }
+        for y := first; y <= last; y++ {
+            img.SetColorIndex(x1, y, ci)
+        }
+    }
+}
+
+func setBackgroundColor(img *image.Paletted, w, h int, ci uint8) {
+    for x := 0; x < w; x++ {
+        for y := 0; y < h; y++ {
+            img.SetColorIndex(x, y, ci)
+        }
+    }
+}
+
+func hsb2rgb(hue, sat, bri float64) (r, g, b int) {
+    u := int(bri*255 + 0.5)
+    if sat == 0 {
+        r, g, b = u, u, u
+    } else {
+        h := (hue - math.Floor(hue)) * 6
+        f := h - math.Floor(h)
+        p := int(bri*(1-sat)*255 + 0.5)
+        q := int(bri*(1-sat*f)*255 + 0.5)
+        t := int(bri*(1-sat*(1-f))*255 + 0.5)
+        switch int(h) {
+        case 0:
+            r, g, b = u, t, p
+        case 1:
+            r, g, b = q, u, p
+        case 2:
+            r, g, b = p, u, t
+        case 3:
+            r, g, b = p, q, u
+        case 4:
+            r, g, b = t, p, u
+        case 5:
+            r, g, b = u, p, q
+        }
+    }
+    return
+}
+
+func main() {
+    const degToRad = math.Pi / 180
+    const nframes = 360
+    const delay = 20 // 200ms
+    width, height := 640, 640
+    anim := gif.GIF{LoopCount: nframes}
+    rect := image.Rect(0, 0, width, height)
+    palette := make([]color.Color, 151)
+    palette[0] = color.White
+    for i := 1; i <= 150; i++ {
+        r, g, b := hsb2rgb(float64(i)/150, 1, 1)
+        palette[i] = color.RGBA{uint8(r), uint8(g), uint8(b), 255}
+    }
+    incr := 0
+    for f := 1; f <= nframes; f++ {
+        incr = (incr + 1) % 360
+        x1, y1 := width/2, height/2
+        length := 5.0
+        img := image.NewPaletted(rect, palette)
+        setBackgroundColor(img, width, height, 0) // white background
+        angle := incr
+        for ci := uint8(1); ci <= 150; ci++ {
+            x2 := x1 + int(math.Cos(float64(angle)*degToRad)*length)
+            y2 := y1 - int(math.Sin(float64(angle)*degToRad)*length)
+            drawLine(img, x1, y1, x2, y2, ci)
+            x1, y1 = x2, y2
+            length += 3
+            angle = (angle + incr) % 360
+        }
+        anim.Delay = append(anim.Delay, delay)
+        anim.Image = append(anim.Image, img)
+    }
+    file, err := os.Create("polyspiral.gif")
+    if err != nil {
+        log.Fatal(err)
+    }
+    defer file.Close()
+    if err2 := gif.EncodeAll(file, &anim); err != nil {
+        log.Fatal(err2)
+    }
+}