[Bug 346474] Re: ImageMagick interprets PGM header incorrectly
broucaries
346474 at bugs.launchpad.net
Sat Jul 21 22:00:07 UTC 2012
** Changed in: imagemagick (Ubuntu)
Status: Triaged => Fix Committed
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https://bugs.launchpad.net/bugs/346474
Title:
ImageMagick interprets PGM header incorrectly
Status in ImageMagick - Convert, Edit and Compose Images:
New
Status in “imagemagick” package in Ubuntu:
Fix Committed
Bug description:
Binary package hint: imagemagick
Ubuntu 8.10
imagemagick 7:6.3.7.9.dfsg1-2ubuntu3
When reading a PGM-P5 (binary) image with a maxval of 256, the
'convert' and 'display' utility, and likely the rest, will interpret
each pixel as one byte, when it should interpret each pixel as two
bytes since 256 is more than 255. This causes vertical stripes and
other nastiness in the image. If maxval is set to 257, everything
works as it should.
Apparently you can only submit one attachment in this bugtracker so users have to host their own files. Download example images from:
http://natrox.ath.cx/imagemagick/lena-255.pgm
http://natrox.ath.cx/imagemagick/lena-256.pgm
http://natrox.ath.cx/imagemagick/lena-257.pgm
Display with imagemagick:
$ display -sample 400% lena-255.pgm
$ display -sample 400% lena-256.pgm
$ display -sample 400% lena-257.pgm
255 and 257 works, 256 breaks.
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