jQuery Active Thumbnail Greyscale

JavaScript
1

OK, so I have a couple of thumbnails on a slider. The current thumbnail slide could be selected by #slider .nivo-controlNav a.active img.

I implemented HTML5 Grayscale Image Hover in my slider thumbnails.

My code is:

<script type="text/javascript">
	
	// On window load. This waits until images have loaded which is essential
	$(window).load(function(){
		
		// Fade in images so there isn't a color "pop" document load and then on window load
		$(".thumbnails").fadeIn(500);
		
		// clone image
		$('.thumbnails').each(function(){
			var el = $(this);
			el.css({"position":"absolute"}).wrap("<div class='img_wrapper' style='display: inline-block'>").clone().addClass('thumbnails_grayscale').css({"position":"absolute","z-index":"998","opacity":"0"}).insertBefore(el).queue(function(){
				var el = $(this);
				el.parent().css({"width":this.width,"height":this.height});
				el.dequeue();
			});
			this.src = grayscale(this.src);
		});

[COLOR="Red"]$("#slider .nivo-controlNav a.active img").removeClass("thumbnails_greyscale");[/COLOR]
		
		// Fade image 
		$('.thumbnails').mouseover(function(){
			$(this).parent().find('img:first').stop().animate({opacity:1}, 1000);
		})
		$('.thumbnails_grayscale').mouseout(function(){
			$(this).stop().animate({opacity:0}, 1000);
		});		
	});
	
	// 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();
    }
	    
</script>

The code highlighted in red I added, but it doesn’t seem to work for some reason.

Can someone help me disable the greyscale effect for the current thumbnail slide, thanks.