This book has so far been about 2D graphics with Canvas using the standard graphics context. You will hear people say that if you want to do 2D graphics then a good way is to use WebGL. The reason is ...

Bitmaps, gifs, jpegs and so on are common in almost all web pages. With Canvas you now work with bitmaps at the pixel level. It's not difficult, but you need to organize things to make it really easy ...