Gradients!!!!!!!!!!! Holy fucking bingle!!

artist/gradient.go

@@ -0,0 +1,45 @@
+package artist
+
+import "image/color"
+
+// Gradient is a pattern that interpolates between two colors.
+type Gradient struct {
+	First  Pattern
+	Second Pattern
+	Orientation
+}
+
+// AtWhen satisfies the Pattern interface.
+func (pattern Gradient) AtWhen (x, y, width, height int) (c color.RGBA) {
+	var position float64
+	switch pattern.Orientation {
+	case OrientationVertical:
+		position = float64(x) / float64(width)
+	case OrientationDiagonalRight:
+		position = (float64(x) / float64(width) +
+			float64(y) / float64(height)) / 2
+	case OrientationHorizontal:
+		position = float64(y) / float64(height)
+	case OrientationDiagonalLeft:
+		position = (float64(width - x) / float64(width) +
+			float64(y) / float64(height)) / 2
+	}
+
+	firstColor  := pattern.First.AtWhen(x, y, width, height)
+	secondColor := pattern.Second.AtWhen(x, y, width, height)
+	return LerpRGBA(firstColor, secondColor, position)
+}
+
+// Lerp linearally interpolates between two integer values.
+func Lerp (first, second int, fac float64) (n int) {
+	return int(float64(first) * (1 - fac) + float64(second) * fac)
+}
+
+// LerpRGBA linearally interpolates between two color.RGBA values.
+func LerpRGBA (first, second color.RGBA, fac float64) (c color.RGBA) {
+	return color.RGBA {
+		R: uint8(Lerp(int(first.R), int(second.R), fac)),
+		G: uint8(Lerp(int(first.G), int(second.G), fac)),
+		B: uint8(Lerp(int(first.G), int(second.B), fac)),
+	}
+}