Rotating equirectangular maps (G'mic script, GIMP and Krita) + Sinusoidal projection

[Naeddyr]

Here is a script to arbitrarily rotate an equirectangular map with roll, pitch and yaw rotations in G'mic.

There are G'mic plugins for GIMP and Krita, and if you're on Ubuntu and getting your GIMP from a 2.10 ppa you should already have it.

Otherwise, you can download G'mic from https://gmic.eu/download.shtml

To install the script, create a text-file with the contents of this paste-bin, named either user.gmic or .gmic depending on the system.
https://pastebin.com/NKN9VEE4

EDIT: MollyJ has provided some fixes for bugs I think might affect people with newer versions of the Gmic plugin (I can't, after months of not touching the thing, even figure out how to update it): https://pastebin.com/6ZuwezVw

If the old version of the script doesn't work, try this one. Should be the same way to install it as a user.gmic or .gmic file :TIDE

user.gmic is for Windows users. You copy that file into a directory where the G'mic plugin can find it. In my test-case, /Users/%username%/AppData/Roaming seemed to work, but this... Isn't reliable, if my googling is correct.

Linux and Mac users just put .gmic into your /~ home folder. Just straight there.

This text file is the single file that G'mic will scan for new scripts, so if you want more scripts that aren't already in the G'mic standard library, you have to append them into the text file (and same if you already have the file installed, you just copy the contents of what I provide here into it).

equirectangular-rotation-tutorial.png

To run the script, open up GIMP or Krita and open a new Equirectangular map image. Technically, you can open anything and the script won't crash or anything, but to test it download something like one of the smaller downloads of this Wikimedia Blue Marble map.

If you don't see the Map Projection subfolder in the list of G'mic scripts, try refreshing all the scripts with the Refresh button on the bottom middle of the window.

The Equirectangular Rotation plugin lets you just rotate an equirectangular map, and is super, super useful to get rid of polar distortion and copy/paste bits and pieces of a map by rotating it so what you want is in the middle and then copying that into the middle of another map. This is basically a streamlined version of my old "getting rid of polar distortion" tutorial here, years and years back, that used the Hugin panorama stitching application.

The Sinusoidal projection plugin is the same, except it outputs the map into a sinusoidal projection, and even slices it if you want.

Don't expect to see many more projections, figuring out the exact black magic invocations for just these two, super simple projections was painful. And that's not even talking about scripting this all in G'mic.

I have tried to keep my scripts as readable as possible, and invite anyone to extend and replace them.