The script creates a cropped image based on the ROI selection on the image.
If the image is a 3D data block, the behaviour depends on the displayed slices. If as single slice is displayed, the image is cropped to the XY area over all planes. If the slice-tool is used to display the sum of multiple slices, then the displayed slice-range is used as a cropping limit in the Z-direction as well.
Pressing the ALT key when running the script brings up some user-dialogs to specify the limits numerically.
Pressing the SHIFT key will replace the image by the cropped version