Your message dated Thu, 03 Jan 2019 14:49:19 +0100
with message-id <87r2dtetr4.fsf@localhost>
and subject line Re: Bug#668476: openimageio-tools: handling of gamma for JPEG
files in "iv" is weird
has caused the Debian Bug report #668476,
regarding openimageio-tools: handling of gamma for JPEG files in "iv" is weird
to be marked as done.
This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
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--
668476: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=668476
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Package: openimageio-tools
Version: 1.0.0+dfsg0-1
Severity: normal
[Sorry if this is a bit long; issues involving image gamma are always
kind of confusing, so I'm trying to be as explicit and verbose as
possible...]
Given:
1. A typical PNG image file, "foo.png", which was encoded using a
standard encoding gamma correction value of 1/2.2 (0.4545), and
has an explicit PNG gAMA chunk recording that value.
2. A JPEG file, "foo.jpg", produced from "foo.png" file using the
imagemagick command "convert foo.png foo.jpg".
3. Another PNG file, "foo2.png", produced from "foo.jpg" using the
imagemagick command "convert foo.jpg foo2.png"; note that foo2.png
_doesn't_ have an explicit gAMA chunk.
Then:
* Most image display programs (imagemagick, eog, geeqie, qiv, ...)
display all of the files identically. In other words, they assume
that the encoding gamma correction value is 1/2.2 (0.4545) for both
JPEG files, and PNG files without an explicit gAMA chunk.
* "iv foo.png" and "iv foo2.png" displays the image "correctly"
(matching what other image-display programs do), suggesting that it
assumes a default encoding gamma correction value of 1/2.2 for PNG
files.
* _However_, "iv iv.jpg" displays the image much too dark, unlike all
other programs. By using the ")" key-command to change the "gamma"
value to 2.2, the image then looks correct.
=> Thus the bug: it appears that iv assumes an encoding gamma
correction of 1.0 for JPEG files, which does not match standard
practice.
[As an aside, the term "gamma" value displayed in the iv GUI is a bit
confusing; it appears to actually be "encoding gamma correction
divided by display gamma correction."]
Thanks,
-Miles
-- System Information:
Debian Release: wheezy/sid
APT prefers unstable
APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable'), (50,
'experimental')
Architecture: amd64 (x86_64)
Kernel: Linux 3.2.0-2-amd64 (SMP w/2 CPU cores)
Locale: LANG=ja_JP.utf8, LC_CTYPE=ja_JP.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages openimageio-tools depends on:
ii libboost-filesystem1.49.0 1.49.0-2
ii libboost-regex1.49.0 1.49.0-2
ii libboost-system1.49.0 1.49.0-2
ii libboost-thread1.49.0 1.49.0-2
ii libc6 2.13-27
ii libgcc1 1:4.7.0-3
ii libgl1-mesa-glx [libgl1] 7.11.2-1
ii libglew1.7 1.7.0-3
ii libglu1-mesa [libglu1] 7.11.2-1
ii libilmbase6 1.0.1-4
ii libjpeg8 8d-1
ii libopenexr6 1.6.1-5
ii libopenimageio1.0 1.0.0+dfsg0-1
ii libpng12-0 1.2.49-1
ii libqt4-opengl 4:4.7.4-3
ii libqtcore4 4:4.7.4-3
ii libqtgui4 4:4.7.4-3
ii libstdc++6 4.7.0-3
ii libtiff4 3.9.6-2
ii libx11-6 2:1.4.4-4
ii libxext6 2:1.3.0-3
ii zlib1g 1:1.2.6.dfsg-2
openimageio-tools recommends no packages.
openimageio-tools suggests no packages.
-- no debconf information
--- End Message ---
--- Begin Message ---
Hi!
On 2012-04-12 at 15:01 (+09), Miles Bader wrote:
> Package: openimageio-tools
> Version: 1.0.0+dfsg0-1
> Severity: normal
>
> [Sorry if this is a bit long; issues involving image gamma are always
> kind of confusing, so I'm trying to be as explicit and verbose as
> possible...]
[...]
No idea when this was fixed (*if* it was fixed; in fact I don't use a
specific version to close the report), but upstream closed the related
issue on GitHub, thus closing the bug report here too.
Cheers.
--
Matteo F. Vescovi
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