Lock Crop window to a multiple of X & Y pixels. (eg. 8x8)

[Euphoria]

In cropping mode, allow there to be an option to make the selected crop window be a multiple of X and Y pixels.
For example, setting 8x8 would make an crop window, whatever size gro in multiples of 8x8, especially useful, in this example, for cropping PNGs or other image formats, well suited to be encoded as JPG images, among other uses.
Equally valuable for XnViewMP