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From: "Alex R. Mosteo" <alejandro@mosteo.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Color gradients lib
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Date: Wed, 09 Feb 2011 09:53:18 +0100
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Date: 2011-02-09T09:53:18+01:00
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Dmitry A. Kazakov wrote:

> On Tue, 08 Feb 2011 11:58 +0100, Alex R. Mosteo wrote:
> 
>> I need to plot some data (2D maps) and I have everything in my drawing
>> library except some readily usable gradients. I was wondering if some Ada
>> library out there has this before making my custom one.
> 
> OK, that is an ill-defined problem because the visual appearance of a
> gradient (linear function of position) depends on the color space you are
> using. The RGB color space is quite unnatural to human eye. L*a*b is much
> better,  but computationally problematic. HLS is a very coarse
> approximation of L*a*b. GtkAda contributions has an implementation of
> improved HLS model.
> 
> http://www.dmitry-kazakov.de/ada/gtkada_contributions.htm#8
> 
> For building a gradient I would convert the end points to IHLS and then
> use linear functions for hue, luminance and saturation between the points.
> The obtained IHLS colors are then converted back to RGB.

Thanks everybody for the discussion. I'm going to try this approach.