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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Color gradients lib
Newsgroups: comp.lang.ada
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Date: Tue, 8 Feb 2011 19:00:08 +0100
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Date: 2011-02-08T19:00:05+01:00
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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.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de