Re: [RFC] Gradient fill options

[Pierre <pie...@gm...>]

On 2/3/07, Hans-Bernhard Br=F6ker <HBB...@t-...> wrote:
> Pierre wrote:
> > On 2/2/07, Hans-Bernhard Br=F6ker <HBB...@t-...> wrote:
> >> To give an example, from an RGB palette defined like this:
> >>
> >> 0.0: blue
> >> 0.5: white
> >> 1.0: red
>
> > I'm not sure to understand the notion of palette in your example.
>
> It's a (principally) continuous mapping from a numeric value (the number
> being displayed) to a colour.  In the case above, it consists of two
> linear paths, one from blue to white, the second from white to red.  The
> idea is to turn a data parameter into a colour, a.k.a. "false-colour
> diagram".  It's how altitude is often displayed on geographical maps
> (green lowlands, brown hills, white peaks, blue ocean).

Thanks for the explanation.

I think the shaded triangle in #39
(http://bugs.libgd.org/?do=3Ddetails&task_id=3D39) should work.

You can keep your mapping and pass the color value of each vertex.
Within a triangle the colors will be inside your range (linear
interpolation from c1 to c2 between two edges).

I put a meaningless example here: http://blog.thepimp.net/misc/gdshading/

The color stop points are in the comments, it is something like a
range -0.25..1.0 used "black blue red yellow".

The results has no special value (besides being a nice shading effect
;), but it may help to see how gdShadedTriangle works and what should
be done to match your needs.

--Pierre