The task is: Image shadow removal is an important topic in image processing. If you feel curious about it, you may take a look here, or just google for it image shadow removal There are also a few questions on SE around it. For example: https://dsp.stackexchange.com/questions/2247/how-can-i-remove-shadows-from-an-image https://stackoverflow.com/questions/9081930/how-to-remove-the-shadow-in-image-b