// Slideshow script

$(window).load(function()
{
	// test for canvas element:
	var supportCanvas = 'getContext' in document.createElement('canvas');
	
	var slides = $('#slideshow li'),
	    current = 0,
		slideshow = { width:0, height:0 };
	
	setTimeout(function()
	{
		if (supportCanvas)
		{
			$('#slideshow img').each(function() 
			{
				if (!slideshow.width)
				{
					slideshow.width = this.width;
					slideshow.height = this.height;
				}
				
				createCanvasOverlay(this);
			});
		}
		
		window.setInterval(function()
		//$('#slideshow').click(function()
		{
			var li = slides.eq(current),
				canvas = li.find('canvas'),
				nextIndex = 0;
			
			// next image
			nextIndex = current >= slides.length - 1 ? 0 : current + 1;
			
			var next = slides.eq(nextIndex);
			
			if (supportCanvas)
			{
				canvas.fadeIn(function()
				{
					next.show();
					current = nextIndex;
					
					li.fadeOut(function()
					{
						li.removeClass('slideActive');
						canvas.hide();
						next.addClass('slideActive');
					});
				});
			}
			else
			{
				current = nextIndex;
				next.addClass('slideActive').show();
				li.removeClass('slideActive').hide();
			}
		}, 2500);
	}, 1000);
	
    function createCanvasOverlay(image)
	{
        var canvas = document.createElement('canvas'),
            canvasContext = canvas.getContext("2d");
		
        canvas.width = slideshow.width;
        canvas.height = slideshow.height;
		
        canvasContext.drawImage(image, 0, 0);

        var imageData = canvasContext.getImageData(0, 0, canvas.width, canvas.height),
            data = imageData.data;
		
        for (var i = 0, z=data.length; i<z; i++)
		{
            data[i] = ((data[i] < 128) ? (2*data[i]*data[i] / 255) :
                        (255 - 2 * (255 - data[i]) * (255 - data[i]) / 255));
            data[++i] = ((data[i] < 128) ? (2*data[i]*data[i] / 255) :
                        (255 - 2 * (255 - data[i]) * (255 - data[i]) / 255));
            data[++i] = ((data[i] < 128) ? (2*data[i]*data[i] / 255) :
                        (255 - 2 * (255 - data[i]) * (255 - data[i]) / 255));

            // After the RGB channels comes the alpha value, which we leave the same.
            ++i;
        }

        // Putting the modified imageData back on the canvas.
        canvasContext.putImageData(imageData, 0, 0, 0, 0, imageData.width, imageData.height);

        // Inserting the canvas in the DOM, before the image:
        image.parentNode.insertBefore(canvas, image);
    }
});