Example of how to manipulate image data pixel by pixel
Using the imageData property it is possible to loop through the pixels of an image and manipulate them in some way. This example has three sliders each controlling the level of each colour channel. Altering the slider changes the amount of each colour copied from the source image to the new altered image. It is a simple example of how to manipulate the pixels of an image but should serve to help you grasp the basics before you go on to create much more complex effects.