08-17-2022, 08:25 AM
Note: this method applies only to bigger images cut out properly (for instance, multiple screenshots of something too big to fit on a screen), not to picture extracts done with a handheld camera/smartphone that are in the realm of panorama software such as Hugin). This method can also give decent results with partial scans, but this assumes that there is very little distortion in the scanner, which isn't always a given.
- You temporarily set the layer at the top to Difference mode. This will show you outlines in both pics where they overlap. Yes, the top layer doesn't show in the areas where there is nothing below it.
- You move the top layer and and when the position is pixel-perfect the overlap goes completely black. In the last stages you can move the layer pixel-by-pixel using the cursor keys (or you can zoom in to some part of the image with many small details)
- You set the top layer back to Normal mode to restore the full image.
- Rinse and repeat for every layer.