Manual Photo Cropping / Resizing within Page

I am trying to find software that would allow visitors to upload a photograph(s) to see how they would look in selected greeting cards or frames. I have the greeting cards scanned and saved in .PNG format with a transparency window for showing the photograph but I need to find a tool that would allow the image to be resized or cropped by the visitor - to best fit the opening in the frame or card. Any thoughts on where I should look or start?

Thanks in advance.

Ron