48772 - Need to sniff & use current gamma value on launch

Status: RESOLVED DUPLICATE of bug 53597

(Core :: Graphics: ImageLib, defect, P3)

Description

[Eli Goldberg]

(submitting per chat with tor. thanks, tor!)

* TITLE/SUMMARY
Mac needs to use sniff & use current gamma value on launch

* STEPS TO REPRODUCE
0) Launch Seamonkey
1) Display <http://www.libmng.com/MNGsuite/png_suite_2_img.html>.

* RESULT
 - What happened

On Macintosh, the reference row (first row) has a darker background color than 
the other rows. According to the test case author (Gerard), this is because:

"Images without gamma-value are handled with the default gamma-
values set by the app (mng_set_dfltxxxxgamma). If not set, the default 
is matching sRGB, which looks fine on Windows and Linux, but will 
look bad on others such as Mac, SGI, etc.

To fix the problem you can hardcode the gamma-values in libmng to 
match the platform it's compiled on, but I strongly suggest using the 
appropriate initialization routines. Full color-correction would be the 
ultimate goal of course."


 - What was expected 

Mozilla should display images using the appropriate gamma value for the platform.

* REGRESSION

 - Occurs On
        Mac OS Seamonkey (8/10/2000 M18 build)		

 - Doesn't Occur On
        Win32/Linux Seamonkey (8/12/2000 M18 build)


* CONFIGURATIONS TESTED

- [Mac] Power Mac G4 (450 Mhz), 256 MB RAM (VM off), 1024x768 (Thousands of 
Colors), Mac OS 9.0

- [Win32] Vectra VL (266 MHz P2), 96 MB RAM, 800x600 (True Color), NT 4.0 SP5.

- [Linux] Vectra VL (266 MHz P2), 96 MB RAM. Red Hat Linux 6.0 (GNOME).

Comment 1

[Henri Sivonen (:hsivonen)]

If gamma correction is implemented for images, it should be implemented for all color 
handling including CSS and HTML Transitional colors. People will be unhappy if they 
can't get matching colors in images and in CSS.

Also the gamma value *should not* be hardcoded based on platform. If gamma 
correction is implemented, the display gamma value should be queried from the OS. For 
example, I am writing this on a computer running Mac OS with display gamma set to 2.2 
(not 1.8).

Comment 2

[tor]

PNGs are already gamma corrected in mozilla, I think.  Bug 44866 addresses
the matter of color correction, mentioning that we should use the platform's
native color and gamma support (Xcms/ColorSync/ICM2).

Comment 3

[Eli Goldberg]

<corrected subject/platform. per tor's comment in bug.>

Comment 4

[tor]

*** Bug 52079 has been marked as a duplicate of this bug. ***

Comment 5

[Andrew Thompson]

Since this effectively renders PNGs *absolutely useless* for what web designers 
actually use them for:
http://hotwired.lycos.com/webmonkey/00/37/index2a.html

I feel strongly this should have a higher priority than it does. However, being 
a realist, I'll add help wanted.

Comment 6

[Terence Tan]

I'd just like to throw my vote behind this bug as well :-)

This is a fairly major issue for Mac web developers... because, given two
identical images, one exported to GIF and the other to PNG, they'll turn out at
different brightnesses. This makes it very hard to integrate PNG images into
normal web pages.

I reckon that, in the absence of any other solutions, it should be hard-coded to
the Mac standard 1.8 (or no correction at all?)... probably 90% of Mac users run
it that way, and at least it ensures consistency with GIF and PNG colours. We
can sort out sniffing and colour-corrections for everything else later.

Comment 7

[tor]

*** This bug has been marked as a duplicate of 53597 ***