From: nospam@needed.invalid   
      
   On Wed, 5/21/2025 3:54 PM, pinnerite wrote:   
   > I haven't had to do this for many years.   
   > Recently I had to copy a leal/religious document to send abroad.   
   > Unfortunately its size wasa greater than my scanner could handle.   
   >   
   > I took several shots with me cellphone. They were clear but   
   > looked like a plumped cushion.   
   >   
   > I use Gimp a great deal but I couldn't fix the pincushion effect.   
   >   
   > If anyone has experience of this I would welcome it.   
   > In caae the need arises again.   
   >   
   > Alan   
   >   
      
   This at least addresses the topic to some extent, as a backgrounder.   
      
   https://usage.imagemagick.org/lens/correcting_lens_distortions.pdf   
      
   *******   
      
   You should have stuck with the scanner. There are panorama   
   softwares that should easily be able to join shots made on   
   a scanner -- as long as they overlap. The software correlates   
   the overlap and tries to assign the best orientation of the pieces.   
      
   A tough one for panoramas, is taking pages out of a map book,   
   scan each page, then feed into a 2D panorama. The reason   
   this does not work, is each page, since the day it was printed,   
   has stretched a different amount in the X and Y direction,   
   via humidity in the air. Even within the sheet, the stretch   
   is not constant across the sheet. The end result, is that   
   "every distortion imaginable" arrives in the stitched result.   
   Huge errors, like two lines not meeting and being an inch   
   apart, when the intention was that they be colinear.   
      
   Starting with a freshly printed version of the book,   
   reduces the effect. But you don't control how fresh a book   
   is, so you don't know how much distortion is already present.   
      
   *******   
      
   But you're not doing that. You are taking a paper, say scanning   
   the four corners, with some overlap, and for the duration of the   
   scans, the paper is a "constant", and the paper should be regenerated   
   in a panorama attempt.   
      
   One issue with panorama softwares, is they are loaded with various   
   "map projections". You want the map projections turned off,   
   when stitching four corner sheets together to make one larger sheet.   
   finding the setting for that can be a pain in the ass. Strange,   
   that such a simple usage case, could be so poorly handled.   
      
      https://en.wikipedia.org/wiki/List_of_map_projections   
      
   Set aside a week for the project :-)   
      
   If you start now, and *keep notes* for the next time, then   
   you will indeed be ready for it. if you don't keep the notes,   
   you'll need another week.   
      
      Paul   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)