html5-canvas Compositing Increase the color contrast with "saturation"
Example
Increase the saturation level of an image with
ctx.globalCompositeOperation = 'saturation';
The amount of the effect can be controled with the alpha setting or the amount of saturation in the fill overlay
// Render the image
ctx.globalCompositeOperation='source-atop';
ctx.drawImage(image, 0, 0);
// set the composite operation
ctx.globalCompositeOperation ='saturation';
ctx.fillStyle = "red";
ctx.globalAlpha = alpha; // alpha 0 = no effect 1 = full effect
ctx.fillRect(0, 0, image.width, image.height);
