javascripthtmlpngbackground-imageclient-side

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

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 in my webpage prototypes, or at least have this "trick" in my toolbox for future use.

The image is like this (taken from http://g.raphaeljs.com/barchart.html):

enter image description here

Now Youtube accomplishes the (embarrassingly identical) same effect by embedding the image in source code:

(on Youtube main page, right click background to display it, then right click the image and "display image properties" [ffox]):

data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAJUAAACVCAAAAAB0....lotsofdata

I tried to discover where this line of code is in the source code, but due to the dynamic creation, I couldn't.

So, my question is: "Is there a way to apply a tiled background to a page, using a png image generated algorithmically CLIENT-SIDE?" (preferrably with javascript)

I am very beginner in webdev and javascript, but I like to base my learning around defined problems to be solved, so this would be a nice way to learn something

Thanks for reading!

UPDATE:

For anyone interested in tile texture generation using javascript, I found this, which seems very interesting:

http://somethinghitme.com/projects/canvasterrain/

http://somethinghitme.com/projects/canvasterrain/js/canvasTerrain.js

Solution

  • 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/