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OPEN  Bug report #26  -  Color dialog and RGB composite values don't show same values
Posted Dec 14, 2012 - updated Apr 08, 2015
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Issue details
  • Type of issue
    Bug report
  • Status
     
    		 Confirmed
  • Assigned to
    Not assigned to anyone
  • Progress
       
  • Type of bug
    Not triaged
  • Likelihood
    Not triaged
  • Effect
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  • Posted by
    Imported User
  • Owned by
    Not owned by anyone
  • Category
    Artwork construction
  • Resolution
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  • Tags
    icon_customdatatype.png color
  • Difficulty
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Issue description
genete:

The color dialog shows three sliders from 0 to 100. If I convert a Color parameter into its RGB components (composite) they don't show the same values. For example RGB = 0.5, 0.5, 0.5 in the color dialog then the composite RGB values gives RGB = 0.217638, 0.217638, 0.217638.

Also the HTML code (I guess hexadecimal value for RGBA in a 00 -- FF range) correspond to the RGB values for the composited ones and not for the decimal numerical values of the color dialog.

Reading about RGB in Wikipedia I see that there is a non linear correspondence between the diplayed color by the computer and the RGB values then there is a non linearity due to gamma correction. See: http://en.wikipedia.org/wiki/RGB_color_model#Nonlinearity

But if it is in that way, it is confusing if you are using the composited values to fine tuning the color. Maybe it is not a bug, but it is confusing that color dialog and composited RGB values don't show the same values.

Carlos
Steps to reproduce this issue
Nothing entered.

#2
Comment posted by
Imported User
Dec 14, 16:17
dooglus:

If you don't want visually linear colors, uncheck file > setup > misc > visually linear colors.

You're probably right about the composite display though - perhaps they should show the visually adjusted numbers as well if that feature (the default) is enabled.

I'll look at it tomorrow.
#3
Comment posted by
Imported User
Dec 14, 16:18
genete:

Ah! I see. Sorry for boring you. Close it once you look at it ... tomorrow.
#4
Comment posted by
Imported User
Dec 14, 16:18
dooglus:

I've looked at it, and I'm tending to think it's OK how it is, but that it needs documenting better. Maybe a FAQ entry will be enough for now.

The color dialog shows color numbers between 0 and 100, and you have the option of having these be visually linear or not.

If you convert colors into their composite parts, you see real numbers, between 0.0 and 1.0, which show the underlying representation.

You could also split it into YUV and see a different set of components.

As it stands, there's no way to use addition or scaling on the composite parts of a color to make it "twice as bright" (visually), since the arithmetic will be done on the non-visually-linear numbers.

Leave the bug open for now I think, to remind that it needs thinking about?

#5
Comment posted by
Imported User
Dec 14, 16:18
dooglus:

Looking at the wikipedia article, isn't synfig backwards, making the colors even less linear than they were before?

If asking a monitor for 0.5 really gives 0.22, then we should be asking for more than .5 when the user sets the color to 50 (out of 100) in linear mode, right?

In Synfig's visually linear mode, if I ask for color 50,50,50, I get composites of 0.218, 0.218, 0.218, which my monitor will display as something like 0.1, 0.1, 0.1?

#6
Comment posted by
Imported User
Dec 14, 16:18
dooglus:

http://dooglus.rincevent.net/synfig/colors.png shows screen shots - the colors are darker with 'visually linear' enabled. And less linear? The left hand 40% looks black on my display in the 'linear' screen shot.
#7
Comment posted by
Imported User
Dec 14, 16:19
genete:

Hi dooglus.

Really I'm not an expert on colors and its related modifications depending on what's the final display device it is used. What I see is that whatever any correction or calibration were done for a particular display device, the color dialog and the RGB composited values "should" be the same. As a user I don't care about what number represent what color. As a user I would like two things:

  1. A wide range of color selection to allow make as much fine color tuning as possible.
  2. The color representation RGB or HTML code to be consistent between one possible input (color dialog) and other (the RGB composited).


Also as a bonus I would like to have a gamma correction and a display device calibration to allow me tune the color space of the animation to the final output.

I don't know how synfig store the color space for the animation but I know that for RAW photographs the camera have a built in color space that you can modify and the final output (on the screen) of the picture is different when you import a RAW photo. Also in the processing software that reads the raw photo you can correct the image using another color space for the final output (the printer or the monitor) that could be different. The final goal is to achieve the most similar colors in the final output as the original image (the one that was captured by your camera). See http://ufraw.sourceforge.net/Colors.html for more info.

Sorry for the speech.