test.js

			var img = new Image();
			var readerCanvas = document.createElement("canvas");
			var ctx = readerCanvas.getContext("2d");
			img.onload = function () {
				ctx.width = this.width;
				ctx.height = this.height;
				ctx.drawImage(this, 0, 0);

				var imgd = ctx.getImageData(0, 0, this.width, this.height);
				var pix = imgd.data;
				var i = 0;
				pixelData = [];
				for (var y = 0; y < this.height; y++) {
					pixelData[y] = [];
					for (var x = 0; x < this.width; x++) {
						pixelData[y][x] = { // some of these values are off by 1
							r: pix[i + 0],
							g: pix[i + 1],
							b: pix[i + 2],
							a: pix[i + 3],
						};
						i += 4;
					}
				}
			};
			img.src = dataURL; // a data url from the local system