function convertAlphaMask (maskObj, dimensions) {
		var convertCanvas = document.createElement('canvas');
		var convertCtx = convertCanvas.getContext('2d');
		var RGBA;

		convertCanvas.width = dimensions.width;
		convertCanvas.height = dimensions.height;
		convertCtx.drawImage(maskObj, 0, 0, dimensions.width, dimensions.height);

		RGBA = convertCtx.getImageData(0, 0, dimensions.width, dimensions.height);

		//alpha data is on each 4th position -> [0+(4*n)] => R, [1+(4*n)] => G, [2+(4*n)] => B, [3+(4*n)] => A
		for (var i = 3, len = RGBA.data.length; i < len; i = i + 4) {
			RGBA.data[i - 1] = RGBA.data[i - 2] = RGBA.data[i - 3] = RGBA.data[i]; //alpha into RGB
			RGBA.data[i] = 255; //alpha is always 100% opaque
		}

		return RGBA;
	}
convert an image's alpha channel into a black & white canvasPixelArray
@param {DOMElement} maskObj
@param {Object} dimensions
@returns {CanvasPixelArray} RGBA