[CREATE] Gradients formulas
olivier.berten at gmail.com
Sat Jan 8 02:20:45 PST 2011
I put the informations I gathered at
Please check and correct ;-)
Le 12/12/10 21:44, Jon Cruz a écrit :
> On Dec 6, 2010, at 2:02 AM, Olivier BERTEN wrote:
>> Well... I guess my question wasn't clear ;-)
>> What I'm looking for are the actual algorithms used for gradients
>> rendering in the different existing rendering engines. In other words:
>> how do I compute the color value of a point in a gradient.
>> Some underlying questions are:
>> How do you deal with middle point? isn't it just another color stop?
> Depending on the mode for the segment (see GIMP blend modes http://wiki.inkscape.org/wiki/index.php/Swatch_Book#Gradient ).
> You probably should think of it more as a control point for the interpolation function.
>> For the software dealing with different color models, how do you deal
>> with "mixed" gradients? from a RGB color to a CMYK color, for instance?
>> The "Color gradient" article on Wikipedia says "In digital imaging
>> systems, colors are typically interpolated in an RGB color space, often
>> using gamma compressed RGB color values, as opposed to linear."
> It really depends on the software. Adobe often will use the color mode/colorspace with the most fidelity. CMYK is a common fallback.
> And even SVG that interpolates in RGB does allow for explicit control of interpolation in either sRGB or linear RGB.
>> Who does
>> gamma compression? How?
>> I guess the best way to know that is to look at the code so here's for
>> Gimp. If you can give me directions for other rendering engines, that
>> would be great. I'd like to get an equivalent of the
>> gimp_gradient_get_color_at for other softwares.
> For other software, things are trickier. However there are specs out there for postscript, PDF, etc. And people like those in #scribus in IRC are quite familiar with them.
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