canvas-pixel-color.js

function getPixelColor(x,y,canvas){ // where canvas is an HTMLCanvasElement
    var ctx = canvas.getContext("2d");
    var idata = ctx.getImageData(0,0,canvas.width,canvas.height);
    var p = ((y*(idata.width*4)) + (x*4));
    var d = idata.data;
    return [d[p],d[p+1],d[p+2]]; // returns an array of that pixel's red, green and blue values
}