Initial data commit

Task/Color-wheel/Go/color-wheel.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+    "github.com/fogleman/gg"
+    "math"
+)
+
+const tau = 2 * math.Pi
+
+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 colorWheel(dc *gg.Context) {
+    width, height := dc.Width(), dc.Height()
+    centerX, centerY := width/2, height/2
+    radius := centerX
+    if centerY < radius {
+        radius = centerY
+    }
+    for y := 0; y < height; y++ {
+        dy := float64(y - centerY)
+        for x := 0; x < width; x++ {
+            dx := float64(x - centerX)
+            dist := math.Sqrt(dx*dx + dy*dy)
+            if dist <= float64(radius) {
+                theta := math.Atan2(dy, dx)
+                hue := (theta + math.Pi) / tau
+                r, g, b := hsb2rgb(hue, 1, 1)
+                dc.SetRGB255(r, g, b)
+                dc.SetPixel(x, y)
+            }
+        }
+    }
+}
+
+func main() {
+    const width, height = 480, 480
+    dc := gg.NewContext(width, height)
+    dc.SetRGB(1, 1, 1) // set background color to white
+    dc.Clear()
+    colorWheel(dc)
+    dc.SavePNG("color_wheel.png")
+}