[GRASSLIST:61] Re: d.rgb question

[Glynn Clements]

Kirk R. Wythers wrote:

> > You need to set the colors to grey scale for the three maps test.1,
> > test.2 and test3.
> > 
> > ie. r.colors map=test.1 golor=gray
> > etc

Actually, you should use color=rules, e.g.

	GRASS:~ > r.colors map=test.1 color=rules
	Enter rules, "end" when done, "help" if you need it.
	Data range is 0 to 255
	> 0 black
	> 255 white
	> end
	Color table for [test.1] set to rules

This will ensure that 0 is black and 255 is white.

Using color=gray will map the lowest existing category to black and
the highest existing category to white; if the map doesn't use the
entire 0-255 range, you will get the wrong result.

Also, you can read the rules from a file with e.g.

	r.colors map=test.1 color=rules < gray.rules

where gray.rules contains:

	0 black
	255 white
	end

-- 
Glynn Clements <glynn.clements at virgin.net>