[magick-users] RE: Barrel / pincushion distortion

[Wolfgang Hugemann]

> First, if you need PTlens to get the calibration values, this does IM no 
> good. You might as well just use PTlens.

I'm sure that you can determine the transformation parameters yourself 
by suitable matchpoints.

> I suppose to calibrate the lens, you could take a picture of a grid and 
> do some least squares analysis to determine the constants.

Yes, something like that.

> Secondly, the link to GIMP is for binaries and not source code. That 
> link would help to look at the code. But I am not sure whether the 
> people at IM would feel comfortable taking and modifying GIMP code.

I didn't suggest to just take GIMP (or whatever) code. But for the 
correction of pincushion distortion there is no straightforward 
mathematical transformation as for the projective transformation. So 
choosing a suitable fit function needs some experience.

I just wanted to say that such fit functions obviously have been tested 
in PTlens and possibly also in GIMP. An analysis of the code used thus 
would be of help.

I will come back to that subject soon.

Greetings from Germany
Wolfgang Hugemann