New color mode

[Emil Assarsson]

Hi

I'm interested in writing a new color mode for gimp. I find the normal
too saturated and would like to make a new more vivid.

I'm new to Gimp development and I think I need to discuss this with
someone before starting. Do anyone got any pointers or information
about how I should proceed with this? Are there any changes to the
code structure that will permit this to be done with a plugin
eventually?

--
Emil
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[Owen-24]

> Hi
>
> I'm interested in writing a new color mode for gimp. I find the normal
> too saturated and would like to make a new more vivid.
>
> I'm new to Gimp development and I think I need to discuss this with
> someone before starting. Do anyone got any pointers or information
> about how I should proceed with this? Are there any changes to the
> code structure that will permit this to be done with a plugin
> eventually?

Hi,

Just wondering what you mean by a "new color mode" (like RGB or
Grayscale)

Or are you thinking about the swatches available. If so, these are
just a text file (look at your palettes) and modify to suit.

Apolgies if I have you completely wrong

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Owen

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[Martin Nordholts-2]

Emil Assarsson wrote:
> Hi
>
> I'm interested in writing a new color mode for gimp. I find the normal
> too saturated and would like to make a new more vivid.
>  

Hi!

Exactly what do you mean by "color mode" here?

Do you mean that the default RGB -> CMYK conversion produces too
saturated colors?

Best regards,
Martin

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[Andrew A. Gill]

On Mon, 29 Jun 2009, Emil Assarsson wrote:
>
> I'm interested in writing a new color mode for gimp. I find the normal
> too saturated and would like to make a new more vivid.

Hmmm...

Saturation (at least in the HSV model) is pretty much a synonym
for vividness.

Are you talking about what you see when you print it out?  Is it
too dark or muddy?  That can also be called saturation, but it's
a different concept, and may be better discussed by the folks
involved in Gutenprint.

If I don't have that right, you might want to look at the
following site:

<http://dba.med.sc.edu/price/irf/Adobe_tg/models/munsell.html>

and make sure you've got the right term.

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[David Gowers]

I'm pretty sure Emil refers to the Color drawing /layer mode and the
way that it tends to 'burn out' colors -- the result of applying a
colorization is often far more vivid than could reasonably be
expected; Basically the same as the bug regarding improvement of Color
mode cf. Photoshop. A few theories have been advanced on how Photoshop
does it; they both agree that an RGB-based application such as the
current HSL application is incorrect, and IIRC argue for either LAB or
YIQ/YCbCr based color application. In my opinion LAB is higher
quality, however YIQ/YCbCr get the job done with acceptable quality
and higher speed.

I can do some visual comparisons sometime soon if needed.

> Exactly what do you mean by "color mode" here?
>
> Do you mean that the default RGB -> CMYK conversion produces too
> saturated colors?
>
> Best regards,
> Martin
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[Martin Nordholts-2]

David Gowers wrote:
> I'm pretty sure Emil refers to the Color drawing /layer mode and the
> way that it tends to 'burn out' colors -- the result of applying a
> colorization is often far more vivid than could reasonably be
> expected; Basically the same as the bug regarding improvement of Color
> mode cf. Photoshop.

This sounds like
Bug 325564 – Layer mode "Color" doesn't work well
http://bugzilla.gnome.org/show_bug.cgi?id=325564

/ Martin

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[Emil Assarsson]

Hi,

I'm sorry that I didn't find the right terms...

I meant the modes that are used to mix colors with layers and brush
like Normal, Dissolve, Multiply, Divide etc...

For instance: Place a high green and a high red area on a canvas. Then
mix them together with a brush set to like 45% Opacity. The mid blend
will be very dull. I want to create an alternative where the blend is
more a combination of color, value and normal where the blend keeps
some more of it's vividness.
I think I have to experiment with this a lot to find the correct
algorithms for it... sometimes I want it to prefer a warm path and
sometimes a cold. I think this mode could mimic the real life oil- and
watercolors a little bit better if I get it right.

--
Emil
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[Emil Assarsson]

I meant desaturated sorry :-P
> I find the normal too desaturated and would like to make a new more vivid.
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[Martin Nordholts-2]

On 06/29/2009 10:31 AM, Emil Assarsson wrote:
> I meant the modes that are used to mix colors with layers and brush
> like Normal, Dissolve, Multiply, Divide etc...
>    

Currently, the Color layer mode when using GEGL is supposed to use the
Hue and Saturation of the upper layer and the Lightness from the lower
layer. Maybe the RGB -> HSL conversion is buggy? We want Color to behave
correctly in GIMP 2.8 when using GEGL for the projection, see
http://bugzilla.gnome.org/show_bug.cgi?id=325564 . It is great that you
want to look at this, and all you have to do is experiment with
different algorithms in
gimp_operation_point_layer_mode_get_new_color_hsl() in
app/gegl/gimpoperationpointlayermode.c.

Good luck!

Best regards,
Martin

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[Emil Assarsson]

On Mon, Jun 29, 2009 at 9:33 PM, Martin Nordholts<enselic@...> wrote:
> Maybe the RGB -> HSL conversion is buggy?

I don't see it as a bug... it's more of a problem. Gimp uses HSL(?)
and PhotoShop /seems/ to use CIELAB for these operations.
This effects all layer modes that uses that color space for
conversions and doesn't work in the same way as PS... Hue, Saturation,
Color and Value.

HSL treats pure yellow by giving it the same lightness as pure purple.
CIELAB treats them more from a human perspective and sets the pure
yellow to be light (lightness) and pure purple as dark.

Helpful tool to visualize it: http://www.cs.rit.edu/~ncs/color/a_spaces.html

I think we need to add conversion tools for the color space and
rewrite those routines (or add new ones) if it should be a goal to
correctly import PS files with layer modes. (This could actually be a
good way to learn some more about the gimp code for me)

Any comments on this?
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Emil
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[Martin Nordholts-2]

On 07/01/2009 08:21 PM, Emil Assarsson wrote:

> On Mon, Jun 29, 2009 at 9:33 PM, Martin Nordholts<enselic@...>  wrote:
>    
>> Maybe the RGB ->  HSL conversion is buggy?
>>      
>
> I don't see it as a bug... it's more of a problem. Gimp uses HSL(?)
> and PhotoShop /seems/ to use CIELAB for these operations.
>
> Any comments on this?
>    

If using a CIE Lab based color space for defining and implementing the
color layer modes gives better looking and more intuitive results, than
that is the color space we shall use.

A patch that uses CIE Lab (or CIE LCH?) for this when using GEGL would
be much appreciated.

  / Martin


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