|
 |
"Vadim Sytnikov" <syt### [at] ru com> schrieb im Newsbeitrag
news:3e2aad1a@news.povray.org...
> Image maps rendered w/o assumed_gamma in the global_settings look
> acceptable. But if you put "assumed_gamma 1" there (as you should,
> actually), you're applying Display_Gamma (2.2 by default) which makes image
> maps way too bright. Since such output conversion to Display_Gamma is
> apparently the right thing to do, the question is what to do with the
> images.
>
This is also my experience.
> The only solution I've been able to discover so far is to load the image
> into Photoshop, select "Image --> Mode --> Assign Profile..." and assign a
> prifile (a "Generic 2.2" or the so-called "Working RGB", which seems to be
> of gamma 2.1 but has the advantage of sparing you conversion questions the
> next time you try to load saved image). Then save the image in PNG format
> and use that image in the "pigment { image_map { png "my_image.png" }}";
> POV-Ray (its libpng) seems to be able to understand stored profile
> perfectly. BTW, converting image *pixels* (from current gamma of 2.2 to
> gamma 1, so that the implicit inverse conversion by POV-Ray would restore
> textures' original outlook) was not even considered, for obvious reasons.
>
To be more exact: Photoshop stores an additional ICC profile to TIFF, PNG,
anf JPG files, but the only program that makes use of the color profiles (that I am
aware) is Photoshop itself. This ICC extension is not documented by Adobe and the
Adobe specification writes that any other application should ignore it. But Photoshop
adds also a 'gamma' chunk to the png file and this is part of the official PNG spec
and
the libpng (and so POV) does use it. The JPG-JFIF header does not support gamma
information.
> So, gentlemen, are there any suggestions? As to me, the only feasible
> solution I can think of is to add support for "gamma <value>" to the
> image_map statement. Relatively simple, and yet should work perfectly.
>
Well, I convert everything to PNG by using my own little piece of software that also
supports gamma information for PNG files.
-Ive
Post a reply to this message
|
|
