I'm working with scanned forms (paper documents). This forms are in html5 canvas. I have some specific images (logos, shapes, rectangles) that I need to know if exists in html5 canvas. Note that the images ar similar but not equal. I'm working with java script So (finally!) my question is: Anyone have any idea or know any library to detect if an image exists on html5 canvas with some percentage of accuracy. Code samples with js are welcome.