By reducing their size at the given border(s) using C++ statements only. Seriously, the term "image" is a bit general. If you have, say, jpeg images, you want to crop them at the box boundary (each box is 8x8 pixels), otherwise it isn't lossless (you wouly have to recrompress, applying the DCT (discrete cosine transform) on different boundarys, ruining the image if the quality isn't very high). Which brings us to the next problem: what exactly do you want to do yourself? Can you use libraries to load (...crop...) and save the images? Otherwise, jpeg is a little bit hard to implement... (except you are familiar with the compression techniques, that is).
crop image 