diff --git a/image/color/color.go b/image/color/color.go
index d763713..bfd5b39 100644
--- a/image/color/color.go
+++ b/image/color/color.go
@@ -18,3 +18,21 @@ func ToRGBA (c color.Color) color.RGBA {
 		uint8(a >> 8),
 	}
 }
+
+// Premultiply applies alpha-premultiplication that colors must apply as per
+// color.Color.RGBA. This is an intrinsically lossy proccess.
+func Premultiply (ur, ug, ub, ua uint32) (r, g, b, a uint32) {
+	return (ur * a) / 0xFFFF,
+		(ug * a) / 0xFFFF,
+		(ub * a) / 0xFFFF,
+		ua
+}
+
+// Unpremultiply reverses alpha-premultiplication that colors must apply as per
+// color.Color.RGBA. This may or may not return the precise original color.
+func Unpremultiply (r, g, b, a uint32) (ur, ug, ub, ua uint32) {
+	return (r / a) * 0xFFFF,
+		(g / a) * 0xFFFF,
+		(b / a) * 0xFFFF,
+		a
+}