PHP Image Operations: Validate and add watermark to uploaded image files

This class can validate and add watermark to uploaded image files.

It takes a given uploaded image file and automatically determines if it is a valid JPEG, PNG, GIF or WBMP image file.

The class can save the image to file in a given directory in a given format that can also be JPEG, PNG, GIF or WBMP.

The output image may be save with a given width and height preserving the original image proportions.

Optionally the class can add a watermark to the image before it is saved.