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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
 =?utf-8?Q?=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Color gradients lib
Date: Tue, 08 Feb 2011 16:18:06 +0100
Organization: Ada @ Home
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Date: 2011-02-08T16:18:06+01:00
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Le Tue, 08 Feb 2011 15:52:24 +0100, Alex R. Mosteo  =

<alejandro@mosteo.invalid> a =C3=A9crit:
> I want a function mapping from some arbitrary values (my data, with it=
s
> 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.
That's easy enough (or else I'm afraid I've missed something), you don't=
  =

even need a library for that. You just need to compute a function for ea=
ch  =

color channels, y =3D f(x), where x ranges from 0.0 to 100.0 and where y=
 is  =

in turn, amount of red, green and blue. Then you use the rounding method=
  =

of your choice to map it to an integer value which will be the value for=
  =

the associated component of the RGB triplet. The most straightforward  =

function would be linear: y =3D y1 + (x * ((y2 - y1) / 100.0)), where y1=
 is  =

the value for the color channel for the cold color and y2 the value for =
 =

the color channel for the warm color. So if your cold color is (1, 0, 0)=
  =

and your warm color is (0, 0, 1), then for x =3D 0.0, you will get (1,0,=
0),  =

for x =3D 100.0 you will get (0,0,1) and for an intermediate value like =
x =3D  =

50.0 you will get (0.5, 0, 0.5). You may even pre-compute this function =
at  =

the application startup, if this does not change during program executio=
n  =

(you may do so, because in the end you will have integer values anyway).=
  =

And voil=C3=A0, there is no magic :)

Or do I missed something ?

-- =

Si les chats miaulent et font autant de vocalises bizarres, c=E2=80=99es=
t pas pour  =

les chiens.

=E2=80=9CI am fluent in ASCII=E2=80=9D [Warren 2010]