[GRASS-dev] why d.vect.thematic won't run on WinGRASS - d.mon problem

[Glynn Clements]

Michael Barton wrote:

> I'm going to try this as soon as I can steal a bit of time. I'm  
> somewhat uncertain how to get the initial PNG for GRASS_PNG_READ.
> 
> I can create a dummy temp map using r.mapcalc and then save it to a  
> PNG using r.out.png. But I need to make sure that it's background is  
> transparent so that the final composite can overlay whatever is in the  
> map display. Any suggestion for how I do that?

You don't actually need to create an initial image; if the file
doesn't exist, any GRASS_PNG_READ=TRUE setting will be silently
ignored. If the file does exist, the dimensions and depth must match
the values of $GRASS_WIDTH, $GRASS_HEIGHT and $GRASS_TRUECOLOR.

You can create a blank image with "d.frame -e" or "d.erase -f". If
GRASS_TRANSPARENT=TRUE, the image will be transparent, otherwise it
will be filled with $GRASS_BACKGROUNDCOLOR. This works both with
direct rendering and the PNG driver. Note that "d.erase" alone is
equivalent to "d.erase color=white". There isn't any way to clear a
portion of the screen to transparent, only the entire screen.

-- 
Glynn Clements <glynn at gclements.plus.com>