You need to write a picture editor by yourself if your customers want to resize, rotate or crop their pictures in your program. Phocasa is a simple program which crop, rotate, resize, flip pictures. You can package it into your program and call it by command line. After clicking "Edit Picture", phocasa will open a window and show that picture, you can crop, rotate, resize the picture now. After some actions, you can click "Complete", and phocasa will save the picture and then return to your main program.
Compatible for any program languages in Windows Platform.