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Here is an image in support of
http://news.povray.org/povray.newusers/thread/%3Cweb.4373f7155849a475ed802ab30%40news.povray.org%3
Briefly put, Mozilla and Firefox on a Linux box, and IE via an rdesktop
session, display my POV-generated PNGs much more brightly than image
viewers and POV's own image previewer display them.
The full rant is available in p.newusers. I sure would appreciate your
advice on this one folks.
Post a reply to this message
Attachments:
Download 'gammadness.jpg' (37 KB)
Preview of image 'gammadness.jpg'
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Ard wrote:
> Here is an image in support of
>
http://news.povray.org/povray.newusers/thread/%3Cweb.4373f7155849a475ed802ab30%40news.povray.org%3
>
> Briefly put, Mozilla and Firefox on a Linux box, and IE via an rdesktop
> session, display my POV-generated PNGs much more brightly than image
> viewers and POV's own image previewer display them.
>
> The full rant is available in p.newusers. I sure would appreciate your
> advice on this one folks.
>
>
>
> ------------------------------------------------------------------------
>
The gamma chunk in PNG images has given me nothing but trouble.
Every browser, every program, seems to (over)compensate for gamma
in a different way. The answer is to make sure the png file has
no gamma chunk in it.
Here is what I do ..
Render/create image to Targa (tga) file. Open said Targa
file in gimp. Save as a PNG from gimp. In the file save dialog,
make sure that the "save gamma" box is NOT checked. Save. You
have just written a png that contains no gamma. End of problem.
--
to all the companies who wait until a large user base becomes
dependant on their freeware, then shafting said happy campers with
mandatory payment for continued usage. I spit on your grave.
Post a reply to this message
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povray nous apporta ses lumieres en ce 2005-11-11 21:35:
> Ard wrote:
>
>> Here is an image in support of
>>
http://news.povray.org/povray.newusers/thread/%3Cweb.4373f7155849a475ed802ab30%40news.povray.org%3
>>
>>
>> Briefly put, Mozilla and Firefox on a Linux box, and IE via an rdesktop
>> session, display my POV-generated PNGs much more brightly than image
>> viewers and POV's own image previewer display them.
>>
>> The full rant is available in p.newusers. I sure would appreciate your
>> advice on this one folks.
>>
>>
>>
>> ------------------------------------------------------------------------
>>
>
> The gamma chunk in PNG images has given me nothing but trouble.
> Every browser, every program, seems to (over)compensate for gamma in a
> different way. The answer is to make sure the png file has
> no gamma chunk in it.
> Here is what I do ..
> Render/create image to Targa (tga) file. Open said Targa
> file in gimp. Save as a PNG from gimp. In the file save dialog, make
> sure that the "save gamma" box is NOT checked. Save. You
> have just written a png that contains no gamma. End of problem.
>
>
If I remember corectly, if you DON'T include "assumed_gamma" then your PNG don't
include gamma
information. Correct me if I'm wrong.
--
Alain
-------------------------------------------------
Christian Science: When shit happens, don't call a doctor - pray!
Post a reply to this message
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Alain wrote:
> povray nous apporta ses lumieres en ce 2005-11-11 21:35:
>
>> Ard wrote:
>>
>>> Here is an image in support of
>>>
http://news.povray.org/povray.newusers/thread/%3Cweb.4373f7155849a475ed802ab30%40news.povray.org%3
>>>
>>>
>>> Briefly put, Mozilla and Firefox on a Linux box, and IE via an rdesktop
>>> session, display my POV-generated PNGs much more brightly than image
>>> viewers and POV's own image previewer display them.
>>>
>>> The full rant is available in p.newusers. I sure would appreciate your
>>> advice on this one folks.
>>>
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
>>
>> The gamma chunk in PNG images has given me nothing but trouble.
>> Every browser, every program, seems to (over)compensate for gamma in a
>> different way. The answer is to make sure the png file has
>> no gamma chunk in it.
>> Here is what I do ..
>> Render/create image to Targa (tga) file. Open said Targa
>> file in gimp. Save as a PNG from gimp. In the file save dialog, make
>> sure that the "save gamma" box is NOT checked. Save. You
>> have just written a png that contains no gamma. End of problem.
>>
>>
> If I remember corectly, if you DON'T include "assumed_gamma" then your
> PNG don't include gamma information. Correct me if I'm wrong.
>
By first rendering to TGA, a file that that cannot have gamma
information in it, you ensure that povray does not include
gamma information.
By loading the TGA (with no gamma in it) and *then* saving from
gimp as already mentioned, in such a way that no gamma is written,
you are assured of a clean no-gamma-info file.
--
to all the companies who wait until a large user base becomes
dependant on their freeware, then shafting said happy campers with
mandatory payment for continued usage. I spit on your grave.
Post a reply to this message
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Alain <ele### [at] netscape net> wrote:
> If I remember corectly, if you DON'T include "assumed_gamma" then your PNG don't
> include gamma information. Correct me if I'm wrong.
I think I'm going to have to correct you there Alain. PNGs generated with
POV-Ray 3.6.1 on Linux include gamma information (a gAMA chunk) whether the
source file contains assumed_gamma or not.
However your suggestion led me to discover the cause of one of my problems:
the value in the gAMA chunk in the PNG is set to 1.0 if a CPU histogram is
generated with +HTx. It should be set to 1/display_gamma.
Post a reply to this message
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