A way to create random-noise background image (png) with javascript?

Question

The new layout of YouTube added a background random-noise which I like very much, having seen almost exactely the same effect on other sites, so I plan to use the same technique

Answer 1

To generate image client-side, I suggest you to have a look to HTML5 canvas element.

You can draw on a canvas with Javascript (even if the canvas element is hidden), and so generate anything you want (including a simple noise tile).

Resource to learn Canvas drawing : https://developer.mozilla.org/en/Drawing_Graphics_with_Canvas

After that, you can export your canvas as URL with the method toDataURL (a string like "data:image/png;base64....") which is interpreted by browsers like a traditionnal url for an image, so you can set it as css background for your body element.

Warning 1 : Canvas is supported by all modern browsers and you can emulate it on IE with ExplorerCanvas - but I don't know if ExplorerCanvas support .toDataURL()

Warning 2 : Canvas is resolution-dependant, so I suggest you to generate a little tile (32*32, or 64*64) and repeat it

Edit : An example of tiled background : http://jsfiddle.net/SfzPc/12/

Edit 2 : An completed example with a noisy background : http://jsfiddle.net/SfzPc/14/