Re: Mapping float values to colors.

[Ken Cline]

On Tue, 27 Jul 1999, Fabio Mascelloni wrote:

> The first problem is that only mappings from unsigned
> chars (Color typedef) to Red,Green,Blue values are
> permitted to build a Colormap, the second is that
> everytime a new matrix is added the mean values
> obviously change, so a new Colormap should be created to
> replace the old one , and assigned to the Raster.

I'm not sure what Marcus would say, but...   have you
considered subclassing Colormap and adding a method like
`setMean:' which perhaps would take a 2D matrix as an 
argument?  The `setMean:' method would then be responsible
for looping thru the provided matrix and updating the
Colormap's `map'.

Colormap is easy to subclass but you should be aware that
the drawing functions (eg tkobjc/internal.m) use the `map'
array directly so it would not be enough to just override a
method like `pixelValue:'.  I'd also suggest either 
overriding `setColor:ToName:' so it doesn't check `colorIsSet:'
or adding a method like `getNameForRed:Green:Blue:' and use
that in conjunction with `tkobjc_setColor'.  (The logic for
a `getNameForRed:Green:Blue:' method can be scooped right
out of `setColorToRed:Green:Blue:', btw.)  Another
alternative that would allow you to reset color is to simply
override `colorIsSet' so it returns `NO'.

If you choose to subclass Colormap, you'll still need to
call Raster's `drawPointX:Y:Color:' and `drawSelf' elsewhere.
You don't gain alot by subclassing but it might make it
easier to debug.  Just an idea.

Cheers.

Ken.

_________________________________________________________
Ken Cline                             address@hidden
SAIC                                 VOICE (410) 571-0413
Annapolis, MD                          FAX (301) 261-8427






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