HTML5 Canvas Performance: Loading Images vs Drawing

Question

I'm planning on writing a game using javascript / canvas and I just had 1 question: What kind of performance considerations should I think about in regards to loading images vs just drawing using canvas' methods. Because my game will be using very simple geometry for the art (circles, squares, lines), either method will be easy to use. I also plan to implement a simple particle engine in the game, so I want to be able to draw lots of small objects without much of a performance hit.

Thoughts?

Answer 1

If you're drawing simple shapes with solid fills then drawing them procedurally is the best method for you.

If you're drawing more detailed entities with strokes, gradient fills and other performance sensitive make-up you'd be better off using image sprites. Generating graphics procedurally is not always efficient.

It is possible to get away with a mix of both. Draw graphical entities procedurally on the canvas once as your application starts up. After that you can reuse the same sprites by painting copies of them instead of generating the same drop-shadow, gradient and strokes repeatedly.

If you do choose to draw sprites you should read some of the tips and optimization techniques on this thread.

My personal suggestion is to just draw shapes. I've learned that if you're going to use images instead, then the more you use the slower things get, and the more likely you'll end up needing to do off-screen rendering.

Answer 2

This article discusses the subject and has several tests to benchmark the differences.

Conculsions

In brief — Canvas likes small size of canvas and DOM likes working with few elements (although DOM in Firefox is so slow that it's not always true).

And if you are planing to use particles I thought that you might want to take a look to Doodle-js.