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So I have two images both of which are maps of the world, however, the size of the continents are slightly off each other as shown below. The question is how do I distort them so that when overlayed they are for the most part equal in their outline. Below I have added both images if you want me to clarify something I wrote please ask.

Link to pictures on Imgur

  • For anyone who happens to stumble upon this and indeed has a distorted image relative to another, but showing the same thing from the same perspective, this correction of distortion is a standard procedure in cartography and done in GIS by georeferencing. You can duckduckgo for a "georeferencing tutorial" with e.g. "QGIS", which is one of the better GIS's out there (might even be the de facto standard for general application). Also, there is the Geographic Information Systems for any questions related to GIS and cartography. – thymaro May 5 '18 at 10:26
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There is ofn-layer-aligner but it has been written for Gimp 2.8. Basically

  • you make a path with 4 points:
    • two on one layer (bottom one, reference)
    • and the matching two on the other (top layer, transformed, must be the active layer)
  • and it scales/rotates/translates the active layer so that the two pair of points overlap.

Works well on your image on Gimp 2.8.

On 2.9 you may be able to use the unified transform tool (not tested):

  • Move the top layer so that one point exactly overlaps its match on the other layer
  • Drag the rotation/scale center (aka pivot) to that point
  • Scale the top layer so that a second point matches
  • Yes, I have used the unified transform before and though it works well enough, I was wondering if there was a more efficient way that involved an automatic process, so that I can get all the things that are hard to see/hard to micro. Will give the ofn-layer-aligner a try though. Thanks! – Politic Revolutionnaire May 24 '17 at 0:47
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I don't think you need to do anything as complex as distorting them. These images are not as irregular as you might think.

The main problem is the images are not the same size. If you check the size of the top image, the width is 3888 pixels, The bottom one's width is 4800px.

If you use Image > Scale image, change the width on one of them to make it match the other ensuring that the aspect ratio is maintained (the link icon), then they almost match up perfectly, except for the vertical positioning.

Then paste one as a layer above the other.

To align them, reduce the opacity of the top layer and use the Move tool to align them.

Screenshot of aligned images

Screenshot of aligned images

  • Yeah, I checked out how it aligned before, but concluded I had to distort in order to fix issues such as the Caspian sea being dramatically different and to ensure they are aligned completely accurate, the problem is that I need a high degree of accuracy in terms of alignment in this particular instance. – Politic Revolutionnaire May 24 '17 at 10:16
  • The Caspian sea is not distorted, it would seem the actual sea matches in both - it's the area of black in the darker image that is different. – Billy Kerr May 24 '17 at 11:47
  • See enlarged area here: i63.tinypic.com/o0cxad.jpg - perhaps these maps are from different times. The Caspian sea has been drying up recently. – Billy Kerr May 24 '17 at 11:55

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