Added a pseudorandom noise pattern

artist/noise.go

@@ -0,0 +1,22 @@
+package artist
+
+import "image/color"
+
+// Noisy is a pattern that randomly interpolates between two patterns in a
+// deterministic fashion.
+type Noisy struct {
+	Low  Pattern
+	High Pattern
+	Seed uint32
+}
+
+// AtWhen satisfies the pattern interface.
+func (pattern Noisy) AtWhen (x, y, width, height int) (c color.RGBA) {
+	special := uint32(x + y * 348905)
+	special += (pattern.Seed + 1) * 15485863
+	random := (special * special * special % 2038074743)
+	fac := float64(random) / 2038074743.0
+	return LerpRGBA (
+		pattern.Low.AtWhen(x, y, width, height),
+		pattern.High.AtWhen(x, y, width, height), fac)
+}

elements/testing/artist.go

@@ -215,6 +215,17 @@ func (element *Artist) Resize (width, height int) {
 			Stroke: artist.Stroke { Pattern: uhex(0x00FF00), Weight: 5 },
 		},
 		element.cellAt(0, 7))
+
+	// 1, 7
+	artist.FillRectangle (
+		element,
+		artist.Noisy {
+			Low:  uhex(0x000000FF),
+			High: uhex(0xFFFFFFFF),
+			Seed: 0,
+		},
+		element.cellAt(1, 7),
+	)
 }
 
 func (element *Artist) lines (weight int, bounds image.Rectangle) {