[magick-users] RE: Barrel / pincushion distortion

[Fred Weinhaus]

I have implemented a script, pinbarrel, to apply or correct 
pincushion and/or barrel distortion. This script was implemented 
according the formula given by Dersch on his page at

http://www.all-in-one.ee/~dersch/barrel/barrel.html

Unfortunately, this had to be implemented using -fx. Therefore it is 
rather slow.

I have made some improvements to the algorithm such that one can 
apply the distortion/correction in either x or y direction or both 
and can apply pincushion in one direction and barrel in the other 
direction.

I changed the order of the coefficients to reverse the assignment of 
a,b,c,d from Dersch, so that the most important coefficients are 
first, ie. a then b then c, then d. In other words, the ones that are 
not likely to be zero are first.

The script and examples can be found on my IM script page at

http://www.fmwconcepts.com/imagemagick/index.html


Fred


NOTE-IMPORTANT:  If this distortion correction is going to be used 
with the same camera and same size images and the coefficients remain 
the same, then it is best to re-implement this as a displacement map 
so that the calculations need not be recomputed each time.