I understand what you're trying to say. But a quality "FAKE" picture really involves considerably more than simply changing the brightness or contrast. After all when you change the contrast/brighness the same happens to the surroundings that happens to the object. A cropped object generally creates a ever-so-fine line where the object was cropped in. Granted you can change the alpha channel and the opacity. Brightness changes are handy though to find details which you normally can not see.