Plasma effect: Difference between revisions

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 Loop</lang>
+=={{header|Go}}==
+This uses Go's 'image' packages in its standard library to create an animated GIF. The file itself can be created from the terminal as follows:
+<pre>
+  $ go build plasma.go
+  $ ./plasma > plasma.gif
+</pre>
+When played this is broadly similar to the Java entry on which it is based. The whole animation completes in 4 seconds and repeats indefinitely.
+Although the .gif works fine in Firefox it might not do so in EOG due to optimizations made during its creation. If so, then the following ImageMagick command should fix it:
+<pre>
+  $ convert plasma.gif -coalesce plasma2.gif
+  $ eog plasma2.gif
+</pre>
+<lang go>package main
+import (
+    "image"
+    "image/color"
+    "image/gif"
+    "math"
+    "os"
+)
+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 = 100
+    const delay = 4 // 40ms
+    w, h := 640, 640
+    anim := gif.GIF{LoopCount: nframes}
+    rect := image.Rect(0, 0, w, h)
+    palette := make([]color.Color, nframes+1)
+    palette[0] = color.White
+    for i := 1; i <= nframes; i++ {
+        r, g, b := hsb2rgb(float64(i)/nframes, 1, 1)
+        palette[i] = color.RGBA{uint8(r), uint8(g), uint8(b), 255}
+    }
+    for f := 1; f <= nframes; f++ {
+        img := image.NewPaletted(rect, palette)
+        setBackgroundColor(img, w, h, 0) // white background
+        for y := 0; y < h; y++ {
+            for x := 0; x < w; x++ {
+                fx, fy := float64(x), float64(y)
+                value := math.Sin(fx / 16)
+                value += math.Sin(fy / 8)
+                value += math.Sin((fx + fy) / 16)
+                value += math.Sin(math.Sqrt(fx*fx+fy*fy) / 8)
+                value += 4 // shift range from [-4, 4] to [0, 8]
+                value /= 8 // bring range down to [0, 1]
+                _, rem := math.Modf(value + float64(f)/float64(nframes))
+                ci := uint8(nframes*rem) + 1
+                img.SetColorIndex(x, y, ci)
+            }
+        }
+        anim.Delay = append(anim.Delay, delay)
+        anim.Image = append(anim.Image, img)
+    }
+    gif.EncodeAll(os.Stdout, &anim)
+}</lang>
 =={{header|Gosu}}==