305091 - png images do not display colours correctly

Status: RESOLVED INVALID

(Core :: Graphics: ImageLib, defect)

Description

[alessio]

User-Agent:       Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.7.7) Gecko/20050416
Build Identifier: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.7.7) Gecko/20050416

when png images are displyed on mozilla browser their colour is lighter than the
actual one. 

Reproducible: Always

Steps to Reproduce:
1.create image (i.e. on photoshop/imageready)
2.save image as PNG
3.open it on mozilla or simply include it in an html page

Actual Results:  
the colours have a lighter hue

Expected Results:  
display the image with it's saved colour

no other browser seems to have the same problem

Comment 1

[u63580]

Could we have a testcase?  You are also using a very old build - please retest
with a current nightly.

Comment 2

[Frank Wein [:mcsmurf]]

BTW: It might be that photoshop uses some color management which so leads to
different colors. Also did you open the PNG file in photoshop/imageready
directly and looked if the colors are still different?

Comment 3

[alessio]

(In reply to comment #2)
> BTW: It might be that photoshop uses some color management which so leads to
> different colors. Also did you open the PNG file in photoshop/imageready
> directly and looked if the colors are still different?

nope, it's just a mozilla display problem. the images are shown correctly on
photoshop and on the other browsers as well 

Comment 4

[alessio]

i've also tested 1.7.11

Comment 5

[u63580]

This is WFM with a variety of pngs on Windows.  Please can you supply a test
image showing the problem.

Comment 6

[Hiro]

dup bug75133 or bug53597 ?

Comment 7

[Arash]

Attachment: Here's a png that doesn't display properly

To see the full test case, go to http://paxdot.com/testcases/pngcolor/. The
image is used as a non-repeating background and is filled in by
background-color: #72C5E3; everywhere else. As a result, you shouldn't see
where the image ends (if it was working properly).

Comment 8

[Arash]

I tested this on Linux, Mac and Windows and it was present in all (using Firefox
1.06). I also tested using Deer Park 2 on Mac and it still failed there.

Comment 9

[Boris Zbarsky [:bzbarsky]]

> http://paxdot.com/testcases/pngcolor/

This times out.  But the attached image does show the problem...

Comment 10

[Boris Zbarsky [:bzbarsky]]

OK, vlad says that png has a gamma of 0.550 set, which is what causes the issue.  So this is invalid.

Comment 11

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

The image has an embedded PNG gAMA chunk of 0.55; per http://lxr.mozilla.org/mozilla/source/modules/libpr0n/decoders/png/nsPNGDecoder.cpp#258 we tell libpng to use that gamma, instead of the default gamma of 0.45455.

We're not as smart about gamma as we should be; however, the fix here is to use a tool like TweakPNG (http://entropymine.com/jason/tweakpng/) and simply delete the gAMA chunk from the PNG (or tell the image creating tool to not output gamma data).