Public Lab Research note

A Method for distorting Mobius Action Cam imagery in GIMP (FOSS)

by eustatic | November 11, 2014 21:31 | 3,232 views | 4 comments | #11336 | 3,232 views | 4 comments | #11336 11 Nov 21:31

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What I want to do

Make Mapknitter maps with infragram and another mobius (so light!)

So Mat suggested a method of distorting graph paper until it looked right.

Chris Fastie has laid out the limitations of infragram maps --the edges need to be cropped

I think GIMP crops edges.

I want to use this because I'm too poor for photoshop, and freedom rules.

My attempt and results

There are two "Lens Distortion" filters in GIMP

Filters -> Distort -> Lens Distortion

"Main" and "Edge"

Here is the original image


Main -40


Main -41 edges +5


Main -42 edges 0


Main -50 edges 0


Questions and next steps

What do people think?

Here's a shoreline map with no distortion, -34, and -41 5.





I was wondering if we could add this as a feature to (and potentially MapKnitter in the future!) by writing a JavaScript Canvas module that removes lens distortion from an image.

I might've thought to do it in the same way we use Canvas to distort (

but these days, we might be able to write a WebGL module to do it even faster.

This person has ported a lens distortion shader ( to WebGL:

The shaders are here:

hmmm! I don't know webgl well, but it seems promising?

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I also do not know webgl, but

this would be an excellent option to those softwares.

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I've been using the Mobius Cam with both standard and Wide Angled Lens for KAP and soon UAV. I solved the lens distortion issue thanks to a workflow suggested to me in the comment section of my KAP research note- (see bottom 3 comments in the thread) Basically, there is a Plugin called "BIMP" that allows you to do batch processing in GIMP. You do need to set the distortion values manually however, by taking a screenshot and copying the values into the plugin dialog. There are other FOSS programs for batch processing like DIGIKAM and HUGIN Panorama editor that I havent tried yet. However, considering the popularity of GIMP, it may be worth designing our own plugin with Mapknitter (and/or Infragram) support as more and more people use the Mobius Cam.

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just getting back into this again. ajawitz, thanks for your BIMP recommendation.

i think i was going to figure out how to batch process

channel switching R-B, red boost to 130, then contrast boost

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