Re: Background color in raster widgets

[Nelson Minar]

>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.