diff --git a/canvas.go b/canvas.go
index 89b5bda..51cd06b 100644
--- a/canvas.go
+++ b/canvas.go
@@ -4,8 +4,9 @@ import "image"
 import "image/draw"
 import "image/color"
 
-// Canvas is like Image but also requires Set and SetRGBA methods. This
-// interface can be easily satisfied using a BasicCanvas struct.
+// Canvas is like draw.Image but is also able to return a raw pixel buffer for
+// more efficient drawing. This interface can be easily satisfied using a
+// BasicCanvas struct.
 type Canvas interface {
 	draw.Image
 	Buffer () (data []color.RGBA, stride int)