[Bf-committers] color space changes

Roger Wickes rogerwickes at yahoo.com
Fri Nov 12 17:27:18 CET 2010

You cannot tell if a color should be treated as linear or gamma-encoded 
until you perform some operation on it.
If you are using linear workflow, 
and If you sample an image from a gamma-corrected image, you should get a linear 
color value, 

which is the actual value but then gamma-corrected for some gamma curve value. 
but if you sample a pixel from a linear image, such as an already-corrected 
(linearlized) photo,
or sample an pixel from a linear pallete for like a texture brush color, you 
should get a linear (the actual) value. 

the problem is that the sampler has no way of knowing if you;re sampling 
a linear-space color swatch like if you were picking a brush color, and return 
the actual pixel value,
or sampling a pixel from a photo and should therefore gamma-correct (gamma .45 
if your using 2.2 (.45=1/2.2)) the value


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----- Original Message ----
From: Kent Mein <mein at cs.umn.edu>
To: bf-committers at blender.org
Sent: Fri, November 12, 2010 10:34:28 AM
Subject: [Bf-committers] color space changes

Hi all,

I was talking to Rant, Author of bug #24559 which was rejected.
He asked me to explain the reason it was rejected.

After looking at it a bit, I'm not so sure we should be rejecting this one.

This has to deal with converting to linear color space.  I think the
current solution is odd to say the least.

Try this little experiment.
Load up the gimp, use the color picker to pick a color.
Something like RGB 113 196 201

paint the entire picture that color and save the file.

Load up blender, and open your image in the image editor.
and use the color sampler to sample the color.
Now in Hex I have color 71C4CA  in both programs.
In RGB though in blender I have .165  .552 .591
Now I get that it's a different color space but if I
had chosen a different work flow, example:
I had used 113 196 201 and converted them to 0.0-1.0 range
I would get totally different numbers, something like:
.441 .765  .785

It might make this simpler if we had a check box in the
color picker for gamma corrected or not.  Default on.
If you unselect it, then you get linear color space, and
all values are converted, (Hex = N/A for uncorrected?)

Anyway what does everyone else think?

The color correction is suppose to make our lives easier,
right now though I'm more confused when looking at colors
between multiple programs.

Links for people that want more info:


mein at cs.umn.edu
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