Bug#1016653: gm(1): targa (.tga) files are read and written upside-down
On Thu, 4 Aug 2022, Bob Friesenhahn wrote: Testing with ImageMagick 6.9.12-38 on an Illumos system shows the image the other way around with the bright pink cone laying on what might be a gray floor. Due to the nature of the image, it is difficult to tell what the right way up is. It appears that ImageMagick 6.9.10-23 and 6.9.12-38 do not display the same output! Thankfully this issue brought my attention back to TGA format. I found that an unnecessary security check was blocking reading some files entirely. I also noticed that the code could be optimized a bit. However, I believe that this bug report is incorrect. What has actually happened is that ImageMagick changed what it returns and more recent ImageMagick also changed what it does when it displays an image. GraphicsMagick always returns an image in the common normal form (TopLeft). ImageMagick changed so that it returns an image in the same form as the file, but it sets an orientation option so that the user needs to use -auto-orient to see a correct image. In the older version of ImageMagick, the 'display' program does not appear to automatically adjust the orientation where as the newer version does. This morning I committed the TGA improvements and created a new development snapshot release. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
Bug#1016653: gm(1): targa (.tga) files are read and written upside-down
Testing with ImageMagick 6.9.12-38 on an Illumos system shows the image the other way around with the bright pink cone laying on what might be a gray floor. Due to the nature of the image, it is difficult to tell what the right way up is. It appears that ImageMagick 6.9.10-23 and 6.9.12-38 do not display the same output! Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
Bug#1016653: gm(1): targa (.tga) files are read and written upside-down
On Thu, 4 Aug 2022, Bob Friesenhahn wrote: On Thu, 4 Aug 2022, László Böszörményi (GCS) wrote: I see that a bit of code in 'tga.c' dealing with image orientation was commented out because the compiler warned that it produced an invalid result. That was unfortunately not attended to. Did you fix it with changeset 16721 [1]? I don't have time to compile and check it ATM, but might package it tomorrow if it's a proper fix. No it is not fixed yet. I fixed a different bug, which caused some sample files to not be read at all. While it would not surprise me all if there is an orientation bug in GraphicsMagick, for the provided case, the image shown by ImageMagick 6.9.10-23 and GraphicsMagick is exactly the same. The orientation which likely has issues is the exceedingly rare case where the row pixels may need to be written in reverse. Can this issue be reproduced independently? Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
Bug#1016653: gm(1): targa (.tga) files are read and written upside-down
On Thu, 4 Aug 2022, László Böszörményi (GCS) wrote: I see that a bit of code in 'tga.c' dealing with image orientation was commented out because the compiler warned that it produced an invalid result. That was unfortunately not attended to. Did you fix it with changeset 16721 [1]? I don't have time to compile and check it ATM, but might package it tomorrow if it's a proper fix. No it is not fixed yet. I fixed a different bug, which caused some sample files to not be read at all. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
Bug#1016653: gm(1): targa (.tga) files are read and written upside-down
Hi Bob, On Thu, Aug 4, 2022 at 9:39 PM Bob Friesenhahn wrote: > On Thu, 4 Aug 2022, Ivan Shmakov wrote: > > While graphicsmagick claims to support ‘Truevision Targa’ > > format, its implementation is apparently slightly defective > > in that the images are read and written with their vertical > > axis reversed. Consider, for instance, SHAPES.TGA from [1]: > > it’s shown with the gray (#9c9c9c) ‘floor’ at the bottom of > > the image by both LDPCXTGA.EXE and ImageMagick’s display(1), > > yet $ gm display SHAPES.TGA shows the floor at the /top/ of > > the image instead. > > I see that a bit of code in 'tga.c' dealing with image orientation was > commented out because the compiler warned that it produced an invalid > result. That was unfortunately not attended to. Did you fix it with changeset 16721 [1]? I don't have time to compile and check it ATM, but might package it tomorrow if it's a proper fix. Thanks, Laszlo/GCS [1] http://hg.graphicsmagick.org/hg/GraphicsMagick/rev/2504f4ed1a52
Bug#1016653: gm(1): targa (.tga) files are read and written upside-down
On Thu, 4 Aug 2022, Ivan Shmakov wrote: While graphicsmagick claims to support ‘Truevision Targa’ format, its implementation is apparently slightly defective in that the images are read and written with their vertical axis reversed. Consider, for instance, SHAPES.TGA from [1]: it’s shown with the gray (#9c9c9c) ‘floor’ at the bottom of the image by both LDPCXTGA.EXE and ImageMagick’s display(1), yet $ gm display SHAPES.TGA shows the floor at the /top/ of the image instead. I see that a bit of code in 'tga.c' dealing with image orientation was commented out because the compiler warned that it produced an invalid result. That was unfortunately not attended to. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
Bug#1016653: gm(1): targa (.tga) files are read and written upside-down
Package: graphicsmagick Version: 1.4+really1.3.38-1 Severity: minor Control: found -1 1.4+really1.3.36+hg16481-2 Control: found -1 1.4+really1.3.35-1~deb10u2 [Please do not Cc: me, for I’m “on the list,” so to say, and I try to reserve my inbox for private communication only. I’d have set up Mail-Followup-To:, but there doesn’t seem to be a way to make it point to the report being filed.] While graphicsmagick claims to support ‘Truevision Targa’ format, its implementation is apparently slightly defective in that the images are read and written with their vertical axis reversed. Consider, for instance, SHAPES.TGA from [1]: it’s shown with the gray (#9c9c9c) ‘floor’ at the bottom of the image by both LDPCXTGA.EXE and ImageMagick’s display(1), yet $ gm display SHAPES.TGA shows the floor at the /top/ of the image instead. [1] http://archive.org/download/simtelnet_bu_mirror_2013_04 /simtelnet.bu.mirror.2013.04.zip/simtelnet%2Fmsdos%2Fgraphics %2Fldpcxtga.zip (URI split for readability.) The same applies to images produced with $ gm convert. The obvious workaround is to use -flip, like: $ gm display -flip SHAPES.TGA $ gm convert input.file -flip output.tga -- FSF associate member #7257 http://am-1.org/~ivan/
