Batch polar coordinate conversion

Question

I need to convert many files of the same size to polar projections. This is easy to do in GIMP with the Polar Coordinates plugin (Filters > Distorts > Polar Coordinates). However, I'm not sure how to either automate or batch this process.

I know that it is possible to script the automation and there is a commonly suggested batch processing plug-in called BIMP. However, both options call the "plug-in-polar-coords" procedure which does not act the same way in script as it does in the GIMP GUI. Below is an example:

I need to go from files that look like this (courtesy of Flickr user gadl (Alexandre Duret-Lutz) under CC BY-NC-SA):

...to images that look like this:

Which I've done with these settings in GIMP GUI:

Now I need to figure out how to do this with multiple images. I tried to use BIMP with the manipulation "plug-in-polar-coords" but it does not provide an option to map the image to a circle as in the Polar Coordinates window (i.e. the "To polar" radio button).

And outputs files that look like this:

Any thoughts on how to do this? I would prefer solutions in GIMP but will also accept solutions in Inkscape.

Answer 1

So I know next to nothing about Gimp, but you could do this in Imagemagick, which as long as you're able to install, should be as easy as copy&pasting the code into the command line and pressing enter.

cd "path to your input folder"
mkdir "../output" 

mogrify \
  -path "../output" \
  -rotate '180' \
  +distort Polar 0 \
  -virtual-pixel 'horizontal-tile' \
  -background 'black' \
  -quality 100 \
  -format jpg *

Explanations

• cd "" - Input path goes here. You should be able to drag a folder into the command line window to get its path.
• mkdir "" - Makes a folder. In this case the output folder.
• mogrify
  • path "" - Path to output folder. ../ traverses one level up from the input folder.
  • rotate - This is used so the polar distort makes a globe. I don't know if distort would have an option for flipping the image but this works.
  • distort Polar - Polar distort
  • virtual-pixel - This option defines what color source should be used if and when a color lookup completely 'misses' the source image.
  • background
  • quality
  • format - Output format.
  • \ is used to split the mogrify command into multiple lines so it's easier to read.

Answer 2

The plug-ins are mostly implementing the Gimp 2.8 GUI. You would just need to set circle depth to 100% and "Polar to rectangular" to "False"

Demonstration: in the Gimp 2.8 UI I get the same output as you with these parameters:

And to get the picture you want I change to these:

To be more complete, using in 2.10 the same API as BIMP: