Merge

Main Menu:
Image > Transform > Merge

Combines two images together to create a merged image. Also you can combine and merge channels from the original image.

Open the first image and then select Image > Transform > Merge to browse for the second image. Then the merge window will appear.

How merge works

The opacity of both images can be set, from 0 (fully transparent) to 255 (fully opaque).

The horizontal and vertical offset moves the front image. Moving the image may be useful  when both images don't have the same size.

A Zoom control is provided here because the normal zoom command is disabled while merging images.