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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: Tue, 08 Feb 2011 15:52:24 +0100
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Yannick Duchêne (Hibou57) wrote:

> Hi Alex,
> 
> Any graphic capabilities requires an output “device”, either memory
> bitmap, screen, image file, and the latter may be bitmap, PNG, JPEG. I
> feel you miss to provide a context here. Are you seeking for a library to
> generate shapes filled with gradient to which kind of output ? This is
> important to know.

Yes, I was a bit scarce on details.

For the output device I have an abstract layer that can output to GTK or a 
simulator or any other backend I could need, so that's not the issue.

I want a function mapping from some arbitrary values (my data, with its 
minimum and maximum values) into the RGB triplets giving that cold-hot 
representation. Let's say:

type My_Data is float range 0.0 .. 100.0;

type RGB_Component is float range 0.0 .. 1.0;
type RGB_Color is record R, G, B : RGB_Component; end record;

function Gradient (Value : My_Data) return RGB_Color;

And that's it. Hope this helps, and thanks for the interest.

Alex.

> Do not know anything about the context, however an idea : is SVG a valid
> option for you ? For graphs, pies, and other formal representations and
> plotted images, SVG is rather good (if no dynamic features is required),
> and it has gradient capabilities:
> http://www.w3.org/TR/SVG/pservers.html
> 
> Otherwise, please tell more about the context and any relevant technical
> details.
> 
> 
> Le Tue, 08 Feb 2011 11:58:00 +0100, Alex R. Mosteo
> <alejandro@mosteo.invalid> a écrit:
> 
>> Hello,
>>
>> 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.
>>
>> I would need one to represent bad/good ranges (e.g. the default gradient
>> blue-cold to red-hot in matlab), and another to show a density of samples
>> (perhaps simple shades of gray).
>>
>> The second one is straightforward, but the first one seems like something
>> pretty standard, so I wouldn't like to create one that is similar but not
>> the same.
>>
>> (e.g. the first example in
>> http://www.mathworks.com/help/techdoc/visualize/f0-18164.html#f0-5919 )
>>
>> Thanks for any suggestions.
> 
>