add jpeg generation, refactor

color.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"image/color"
+	"math/rand"
+	"time"
+)
+
+type colorFunc func(float64, float64, time.Time) color.Color
+
+func newColorFunc(c colormode) colorFunc {
+	start := time.Now()
+	return func(x, y float64, t time.Time) color.Color {
+		var (
+			r, g, b, a uint8
+		)
+
+		switch c {
+		case crandom:
+			r = uint8(rand.Intn(256))
+			g = uint8(rand.Intn(256))
+			b = uint8(rand.Intn(256))
+			a = 255
+
+		case ctimed:
+			n := time.Since(start).Nanoseconds()
+
+			r = uint8(n % 256)
+			g = uint8((n + 128) % 256)
+			//b = uint8((n + 1) % 256)
+
+			a = 255
+
+		case crainbow:
+			r = uint8(y * 256)
+			g = uint8(x * 256)
+			b = uint8(((y - x) - min(x, y)) * 256)
+
+			a = 255
+
+		default:
+			r, g, b, a = 0, 153, 0, 255
+		}
+
+		return color.RGBA{r, g, b, a}
+	}
+}