Canvas reference: The getImageData function

The getImageData function fetches per-pixel information from the canvas

The getImageData function allows to retrieve an ImageData object from your canvas. This allows you to manipulate it as you wish and then you can add it back on to the canvas with the putImageData function. You can pass it the X/Y/W/H that you want to fetch as arguments.

Arguments to the function

An example

    window.onload = function ()
        var canvas = document.getElementById('cvs');
        var context = canvas.getContext('2d');
        // Fetchs image data from the canvas
        var imgData = context.getImageData(0,0,600,250);