Re: Background color in raster widgets

[Sven N. Thommesen]

At 03:50 PM 1/7/97 -0500, Nelson Minar wrote:
>>I'd like to display my (heat)bugs on a white background rather than pitch
>>black. The black background looks pretty awful when I try to print or make
>>transparencies.
>
>There are two different places that black is being drawn. The Raster
>widget has its own background colour - that can be set. But in
>addition, the entire 2d grid is drawn on the Raster, effectively
>wiping out all background colour. In heatbugs, the brightness of red
>indicates how much heat there is at a spot. So black is 0 red, which
>is entirely cold. You could invert the whole colour scale (move from
>white to red instead of black to red), but if you just remap pure
>black to pure white it's going to look weird.
>
>If you're only concerned about printing, it might be easiest just to
>invert the value channel on the image before printing. Photoshop can
>do this trivially, and maybe xgrabsc or something can.
>
>But if you want to know how to control display in more detail..
>
>>I have tried to read Value2dDisplay and its superclasses, but I just can't
>>seem to locate the spot where those squares get set to black.
>
>Somewhere, I think in Object2dDisplay, there's an object that defines
>the mapping between the Discrete2d values and their colourtable
>entries. It's a linear mapping. You can either change this mapping, or
>else just redefine the colourmap.
>

Nelson,
thanks for tuning in!
As indicated in my earlier post, I did redefine the background color for
Raster, with limited success. I also saw the code for translating heat
values to color values; my app uses color values > 64. I redefined color#0
as white, just to be sure, but to no avail :-(
We'll see if Barry's suggestion pans out.

Cheers,
Sven