🚀 go-pugleaf

|> Hi,
|> 
|> I'm trying to convert a colour (AutoCAD "slide" format) file into
|> a *monochrome* sun rasterfile.  I can use PBMplus to do the job thus:
|> 
|> 	bash$ sldtoppm -adjust file.sld |
|> 	      ppmtopgm |
|> 	      pgmtopbm |
|> 	      pbmtorast > file.ras
|> 
|> The above works, but it appears that the process involves *dithering*
|> the colour image (I suppose "pgmtopbm" does this).  I really don't want
|> dithering, since the final image comes out looking too grainy.  My
|> original colour images contain only *six* colours (they are simple plan
|> diagrams of buildings and campuses).  What I would like to do is
|> translate anything that is not black from the original into white.
|> Something like:
|> 
|> 	INPUT		   OUTPUT
|> 	black (0)	-> black (0)
|> 	non-black (1-?)	-> white (1)
|> 
|> This way, the output should sharper.  All I want is for the walls
|> of buildings and roads to show up clearly.  Is there some alternative way of
|> performing the conversion, so that no dithering is involved?
|> 

Pgmtopbm uses floyd-steinberg dithering by default.  You want thresholding.
Change the call from "pgmtopbm" to "pgmtopbm -threshold -value 0.1", and
try it out.  The "-value" flag sets the level of the threshold: 0.1 means
values above 0.1 get set to white.

-------
Brian C. Smith				arpa:  bsmith@cs.Berkeley.EDU
University of California, Berkeley	uucp: uunet!ucbvax!postgres!bsmith
Computer Sciences Department		phone: (510)642-9585