/* HTML5 Grayscale Image Hover via http://webdesignerwall.com/tutorials/html5-grayscale-image-hover
 * Edited for use within the Gravity theme by NimbleHost
 */
$gravity(window).load(function(){
	var cnvs = document.createElement('canvas');
	if ( cnvs.width ) {
		// Fade in images so there isn't a color "pop" document load and then on window load
		$gravity(".imageStyle").fadeIn(500);
		
		// clone image
		$gravity('.imageStyle').each(function(){
			var el = $gravity(this);
			el.css({"position":"absolute"}).wrap("<div class='img_wrapper' style='display: inline-block'>").clone().addClass('img_grayscale').css({"position":"absolute","z-index":"98","opacity":"0"}).insertBefore(el).queue(function(){
				var el = $gravity(this);
				el.parent().css({"width":this.width,"height":this.height});
				el.dequeue();
			});
			this.src = grayscale(this.src);
		});
		
		// Fade image 
		$gravity('.imageStyle').mouseover(function(){
			$gravity(this).parent().find('img:first').stop().animate({opacity:1}, 500);
		})
		$gravity('.img_grayscale').mouseout(function(){
			$gravity(this).stop().animate({opacity:0}, 500);
		});
	}
});

// Grayscale w canvas method
function grayscale(src){
	var canvas = document.createElement('canvas');
	var ctx = canvas.getContext('2d');
	var imgObj = new Image();
	imgObj.src = src;
	canvas.width = imgObj.width;
	canvas.height = imgObj.height; 
	ctx.drawImage(imgObj, 0, 0); 
	var imgPixels = ctx.getImageData(0, 0, canvas.width, canvas.height);
	for(var y = 0; y < imgPixels.height; y++){
		for(var x = 0; x < imgPixels.width; x++){
			var i = (y * 4) * imgPixels.width + x * 4;
			var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;
			imgPixels.data[i] = avg; 
			imgPixels.data[i + 1] = avg; 
			imgPixels.data[i + 2] = avg;
		}
	}
	ctx.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);
	return canvas.toDataURL();
}