03-08-2022, 10:04 AM
Yes, that is a very nice and clear demonstration.
Perhaps I could explain how my need arises. I am manually stitching together a very large scanned document (The game board for the old board game Civilization by Avalon Hill, which I later plan to attach to some plywood for personal use). I am doing the piecewise scanning at 1200 dpi using an Epson Perfection v850 Pro scanner so that I can capture enough detail to perfectly align the individual scans, at least in theory. In addition to some shearing, the scanner systematically introduces a small but clearly observable trapezoidal distortion, which I need to correct, and thus my need.
In reality, it is difficult to know for certain whether the distortion is a two-dimensional perspective distortion or a one-dimensional trapezoidal distortion. I guess that both could be possible, or it could be a mix, depending on how the distortion arises in the scanning process. And in the end, after applying Median Blur to even out the original screen printing dots, it may make little practical difference which correction method is used, but it is nice to have both available. Initially at least, I would like to try and correct the distortion just along one dimension with a minimal effect on the image along the other, and see how that works out.
Krita seems to be able to natively handle the rather large scan files nicely, while the g'mic plugin also mentioned above is much too slow and unwieldy. A slow script would most likely be equally impractical.
At any rate, this project will be lengthy, slow, and fraught with challenges, and may never come to fruition. The ongoing first step is just to get the scan files aligned as well as possible. The more I try to use an excessively perfectionist approach in the beginning, the more confidently I can move on.
Perhaps I could explain how my need arises. I am manually stitching together a very large scanned document (The game board for the old board game Civilization by Avalon Hill, which I later plan to attach to some plywood for personal use). I am doing the piecewise scanning at 1200 dpi using an Epson Perfection v850 Pro scanner so that I can capture enough detail to perfectly align the individual scans, at least in theory. In addition to some shearing, the scanner systematically introduces a small but clearly observable trapezoidal distortion, which I need to correct, and thus my need.
In reality, it is difficult to know for certain whether the distortion is a two-dimensional perspective distortion or a one-dimensional trapezoidal distortion. I guess that both could be possible, or it could be a mix, depending on how the distortion arises in the scanning process. And in the end, after applying Median Blur to even out the original screen printing dots, it may make little practical difference which correction method is used, but it is nice to have both available. Initially at least, I would like to try and correct the distortion just along one dimension with a minimal effect on the image along the other, and see how that works out.
Krita seems to be able to natively handle the rather large scan files nicely, while the g'mic plugin also mentioned above is much too slow and unwieldy. A slow script would most likely be equally impractical.
At any rate, this project will be lengthy, slow, and fraught with challenges, and may never come to fruition. The ongoing first step is just to get the scan files aligned as well as possible. The more I try to use an excessively perfectionist approach in the beginning, the more confidently I can move on.