On 12.08.2010 01:17, Edward Coffey wrote:
My understanding of GEGL (and, I assume, a fully GEGL-based GIMP) is
that colors will be represented internally as linear-light RGB(A)
structures.
yep. scRGB is the color space of choice according to gegl.org.
(I don't know wether that's the final
On 12 August 2010 00:17, Edward Coffey edward.cof...@gmail.com wrote:
My understanding of GEGL (and, I assume, a fully GEGL-based GIMP) is
that colors will be represented internally as linear-light RGB(A)
structures. Given that (and please correct me if I'm already veering
off track), how are
Thanks a lot for all the input.
I have been using the matrices from
http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html *)
and thought I was doing sRGB/D65-to-Lab or sRGB/D50-to-Lab.
But as I understand now, I was actually doing sRGB-to-Lab/D65 or /D50;
while all the RGB spaces
On 08/11/2010 11:20 PM, yahvuu wrote:
Me, too, thinks that sRGB is a reasonable assumption. If you want to Do It
Right(tm),
you will have to take the image's color profile into account. Since most, if
not all
8-bit implementations of color operations are agnostic of the current color
Rupert Weber wrote:
D50 vs D65
==
Another question during transformation to Lab is, which illuminant or
reference white to use.
The whole point of L*a*b* as a color adjustment space, is that 100,0,0
is the white that the observer is adapted to, ie. RGB = 100%, 100%, 100%.
That's why
Rupert Weber wrote:
(Then again, nobody complained so far and probably nobody would ever
notice if we did it Right(tm)...)
You've got a catch 22 situation: If Gimp doesn't handle color
conversions accurately, then noone interested in accurate
color transforms will use it, hence you will get no
On 12.08.2010 13:09, Rupert Weber wrote:
On 08/11/2010 11:20 PM, yahvuu wrote:
Me, too, thinks that sRGB is a reasonable assumption. If you want to Do It
Right(tm),
you will have to take the image's color profile into account. Since most, if
not all
8-bit implementations of color
On 08/12/2010 12:32 AM, James Cox wrote:
sRGB has only been around since 1996. I suspect that the gimp version
dates from before that, or at least before sRGB came into common use.
That would certainly explain it.
I don't think we want our color profiles to affect layer blending, so I
think
On 12.08.2010 12:52, Rupert Weber wrote:
Thanks a lot for all the input.
I have been using the matrices from
http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html *)
and thought I was doing sRGB/D65-to-Lab or sRGB/D50-to-Lab.
But as I understand now, I was actually doing
Can of worms...
A second attempt at summary and proposed action:
1. D50 vs D65 doesn't make any difference as long as Lab values aren't
communicated to the outside. (E.g. by saving to a file or by having a
Lab color picker)
2. The 'natural' conversion for sRGB seems to be D65. So I'll use
Regarding BABL: i've had a look at extensions/CIE.c and found conversion
routines
using linear light RGB with the sRGB primaries and white point -- that is
scRGB.
Everything fine here.
Now i'm not familier with BABL -- possibly i've checked at the wrong routines?
What I found was
On 12.08.2010 14:46, Rupert Weber wrote:
On 08/12/2010 12:32 AM, James Cox wrote:
sRGB has only been around since 1996. I suspect that the gimp version
dates from before that, or at least before sRGB came into common use.
That would certainly explain it.
I don't think we want our color
On 08/12/2010 03:41 PM, yahvuu wrote:
[...]
So, i think GIMP should Get It Right for GEGL processing, while certain
deviations of
operations' characteristics are tolerable for 8-bit processing.
Fine with me.
Regards
Rupert
___
Gimp-developer
yahvuu wrote:
I guess pretty much everyone agrees that ideally the color profiles of
imported images
should neither affect layer blending nor any tool's characteristics.
The whole point of color profiles is to describe how to interpret the
device values as visual colors. So a tool that
As an end user with no expertise in what is being said in this discussion I
would like to ask three questions:
1. Why such focus on Lab, which seems to be problematic? Why can't YCbCr ITU
R470 or R709 be used? They work without issues for luminance transfer in
Decompose/Recompose. I'm sure
On 12.08.2010 16:16, Graeme Gill wrote:
yahvuu wrote:
I guess pretty much everyone agrees that ideally the color profiles of
imported images
should neither affect layer blending nor any tool's characteristics.
The whole point of color profiles is to describe how to interpret the
device
On 12.08.2010 17:20, yahvuu wrote:
than on import. I mean, if the device color profile isn't known, the
data can't even be displayed
without getting misinterpreted, left alone proccessed.
oh, stop. Got it myself: e.g. for profiling the screen.
Give me a second chance .-)
regards,
yahvuu
2nd take:
On 12.08.2010 16:16, Graeme Gill wrote:
yahvuu wrote:
I guess pretty much everyone agrees that ideally the color profiles of
imported images
should neither affect layer blending nor any tool's characteristics.
The whole point of color profiles is to describe how to interpret the
Graeme Gill wrote:
yahvuu wrote:
The only sane way to achieve this is, like James says, to choose a
single color space
and stick with it. This is possible with floating point processing
(GEGL).
All imported image data gets convert to, say scRGB, processing take
places, and on export
data
yahvuu wrote:
OK, here i'm silently presuming that GIMP is fed with absolute color
data (meaning
that the device color profile is known in case device dependend colors
are given).
Sorry, your statement:
The only sane way to achieve this is, like James says, to choose a single
color
James Cox wrote:
I think it is important to remember that these visual adjustments that we
are applying are really just abstract mathematical formulas that we find
visually useful. In some cases this is quite explicit (eg the multiply
blend mode), and sometimes we try to hide this (eg
Date: Thu, 12 Aug 2010 18:58:45 +0200
From: yahvuu yah...@gmail.com
OK, here i'm silently presuming that GIMP is fed with absolute
color data (meaning that the device color profile is known in case
device dependend colors are given). In my regard, that is 'normal
operation'.
On 12 August 2010 00:17, Edward Coffey edward.cof...@gmail.com wrote:
My understanding of GEGL (and, I assume, a fully GEGL-based GIMP) is
that colors will be represented internally as linear-light RGB(A)
structures. Given that (and please correct me if I'm already veering
off track), how are
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