I\'m creating an HTML5 canvas game for iPhone. I would like to support both retina and non-retina displays.
My question is, how do I support both retina and non-retina d
A new article has just been published on the topic over at html5rocks.com:
upsize your canvas width and height by devicePixelRatio / webkitBackingStorePixelRatio and then use CSS to scale it back down to the logical pixel size you want. Taking our above case where Chrome reports a webkitBackingStorePixelRatio of 1 and a devicePixelRatio of 2 we would scale the dimensions of the canvas by 2 / 1, i.e. multiply them by 2, then we would use CSS to scale it back down.
You use devicePixelRatio to separate retina displays from normal displays
Your game logic coordinates (sprite positions, etc.) must operate independently from the screen coordinates which will be always 2x multiplied on the retina display.
Your graphics assets must have two versions. High resolution version and 50% scaled down normal version. When you operate on retina display, you draw 2x size canvas, resized with CSS and on this canvas use high resolution assets.
I know this is now an old post but thought I'd update it with the solution I implemented.
1: I used two sets of images:
depending on what device is being used depends on what set is loaded.
2: I then resize the canvas (this is the key to it)
NON RETINA
var canvas = document.createElement('myCanvas');
canvas.width = 320;
canvas.height = 480;
canvas.style.width = "320px";
canvas.style.height = "480px";
RETINA
var canvas = document.createElement('myCanvas');
canvas.width = 640;
canvas.height = 960;
canvas.style.width = "320px";
canvas.style.height = "480px";
Notice that canvas.style.width
& height
are the same regardless whether you're using retina or not.
And that's really all there is to it!