Hi,
Some GIMP3 APIs demand Gegl.color value as argument. However I can’t find any example of Gegl.color value.
It seems that it is not (255, 255, 255) , (1.0, 1.0, 1.0) or hex format like “#FFFFFF”. What is the value format?
This? Gegl.Color
I know that, but just don’t know how to enter any value as Gegl.color. What is the format “GeglColorPrivate*`”? How can we describe white as a Gegl.color, for example?
I have solved the problem by myself.
Solution is as below.
color = Gegl.Color.new(“hex format color number”)
And input this variable “color” as argument of the API.
for example, white is
color = Gegl.Color.new(“#FFFFFF”)
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Once you have a color, you can set its components with
color.set_rgba(.1,.2,.3,1.0) # Linear values
color.set_rgba_with_space(.35,.48,.58,1.0,Babl.space('sRGB')) # Gamma-encoded values
Similarly you can also get the linear or gamma-encoded RGBA values with get_rgba() and get_rgba_with_space() (which is also a roundabout way to perform linear⇆SRGB conversions).
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Thank you for your advice!
To initialize variable color, is the following code correct?
color = Gegl.Color.new()
EDIT: @Ofnuts corrected me, you need a parameter.
You can also use some common color names, like
color = Gegl.Color.new("red") or color = Gegl.Color.new("transparent")
Yes, that works.
>>> c=Gegl.Color.new()
Traceback (most recent call last):
File "/Gimp-dev/3.00/run/lib/x86_64-linux-gnu/gimp/3.0/plug-ins/python-console/pyconsole.py", line 797, in do_command
eval(code, self.locals)
File "<input>", line 1, in <module>
TypeError: Gegl.Color.new() takes exactly 1 argument (0 given)
For the names I assume these are the ones I find in the source code?
/* These color names are based on those defined in the HTML 4.01 standard. See
* http://www.w3.org/TR/html4/types.html#h-6.5
*
* Note: these values are stored with gamma
*/
static const ColorNameEntity color_names[] =
{
{ "black", { 0.f, 0.f, 0.f, 1.f } },
{ "silver", { 0.75294f, 0.75294f, 0.75294f, 1.f } },
{ "gray", { 0.50196f, 0.50196f, 0.50196f, 1.f } },
{ "white", { 1.f, 1.f, 1.f, 1.f } },
{ "maroon", { 0.50196f, 0.f, 0.f, 1.f } },
{ "red", { 1.f, 0.f, 0.f, 1.f } },
{ "purple", { 0.50196f, 0.f, 0.50196f, 1.f } },
{ "fuchsia", { 1.f, 0.f, 1.f, 1.f } },
{ "green", { 0.f, 0.50196f, 0.f, 1.f } },
{ "lime", { 0.f, 1.f, 0.f, 1.f } },
{ "olive", { 0.50196f, 0.50196f, 0.f, 1.f } },
{ "yellow", { 1.f, 1.f, 0.f, 1.f } },
{ "navy", { 0.f, 0.f, 0.50196f, 1.f } },
{ "blue", { 0.f, 0.f, 1.f, 1.f } },
{ "teal", { 0.f, 0.50196f, 0.50196f, 1.f } },
{ "aqua", { 0.f, 1.f, 1.f, 1.f } },
{ "none", { 0.f, 0.f, 0.f, 0.f } },
{ "transparent", { 0.f, 0.f, 0.f, 0.f } }
};
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Huh - I could have swore I did that before in C, but maybe I’m misremembering. Thanks for checking! And yes, those can be used.
EDIT: Ah, right, it’s NULL that works.
GeglColor *color = gegl_color_new (NULL)
There does have to be a parameter. I’m not sure if None would work in Python.
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Thank you again! Your advice is very helpful!
Well, not in Python it seems:
>>> c=Gegl.Color.new(None)
Traceback (most recent call last):
File "/Gimp-dev/3.00/run/lib/x86_64-linux-gnu/gimp/3.0/plug-ins/python-console/pyconsole.py", line 797, in do_command
eval(code, self.locals)
File "<input>", line 1, in <module>
TypeError: Argument 0 does not allow None as a value
Thank you.
It seems following code is acceptable in Python.
c=Gegl.Color.new(“”)
It looks like the documentation needs some improvements. 
I got how to set the color, tried with hex it worked, but I have no idea how to GET the color.
I tried all these:
color = Gimp.context_get_foreground()
print(color)
float_rgba = color.get_rgba()
print(float_rgba)
float_hsva = color.get_hsva()
print(float_hsva)
float_hsla = color.get_hsla()
print(float_hsla)
float_cmyk = color.get_cmyk()
print(float_cmyk)
print(color.dict)
print(dir(color))
print(vars(color))
print(color.list_properties())
It seems to me there is no way to get the hex rgb, and get_rgba gives something completely different from the hex in gimp. It should be 66,232,141 and I get:
(red=0.05448118969798088, green=0.8069566488265991, blue=0.26635706424713135, alpha=1.0)
(hue=0.40863433480262756, saturation=0.7155155539512634, value=0.9098062515258789, alpha=1.0)
(hue=0.40863433480262756, saturation=0.7830228805541992, lightness=0.5843158960342407, alpha=1.0)
(cyan=0.9324856400489807, magenta=0.0, yellow=0.6699240207672119, key=0.6699240207672119, alpha=0.193043053150177)
These are the linear values (in the [0.0 ... 1.0] range) of the gamma-encoded(*) values (66, 232, 141).
If you want gamma-encoded values in the [0 ... 255] range:
# just showing we are using the same color (same linear values as yours)
>>> fg.get_rgba()
(red=0.054480597376823425, green=0.8069544434547424, blue=0.26635631918907166, alpha=1.0)
# get the gamma-encoded version ([0.0 ... 1.0] range)
fgSrgb=fg.get_rgba_with_space(Babl.space('sRGB'))
>>> fgSrgb
(red=0.25882428884506226, green=0.9098048806190491, blue=0.5529418587684631, alpha=1.0)
# Scale to the [0 ... 255] range
>>> [x*255 for x in fgSrgb]
[66.00019365549088, 232.0002445578575, 141.0001739859581, 255.0]
Note that you almost never deal with the [0..255] values, unless you want to show/accept them to/from the user.
For some more info: What is the gamma encoding and why are my color computations wrong?
(*) more properly: sRGB-encoded
You are a savior. I was mapping the expected and received and noticed the power law, and down the rabbit hole learning about gamma encoding I found one of your other post explaining this.
You got it exactly right, I need to show the color to the user. More precisely I’m modding for a game where the color encodes regions. So the rgb values end up in a big csv, and I need this to go image > csv.
You’re most welcome. It took me a while to understand this too.