r.colors - was Re: [GRASS-dev] Re: grass-dev Digest, Vol 29, Issue 62

GRASS GRASS developer
1

On Tue, Sep 23, 2008 at 9:28 PM, Glynn Clements
<glynn@gclements.plus.com> wrote:

Michael Barton wrote:

> the manual of 6.4 r.colors says:
> "The rules color table type will cause r.colors to read color table
> specifications from standard
> input (stdin) and will build the color table accordingly.
> "
>
> r.colors help | grep rules
> ...
> color Type of color table
> options: aspect,aspectcolr,bcyr,bgyr,byg,byr,curvature,
>
> differences,elevation,etopo2,evi,grey,grey1.0,grey255,
>
> gyr,ndvi,population,rainbow,ramp,ryb,ryg,sepia,slope,
> srtm,terrain,wave,random,grey.eq,grey.log,rules
> ...
> rules: create new color table based on user-specified rules
> ...
> rules Path to rules file
>
> but:
>
> r.colors map=gpcp_1dd_p1d.2002_sum color=rules rules=color_tab.col
> ERROR: "color", "rules", and "raster" options are mutually exclusive

This shouldn't cause this error. It seems to think that the raster
option has been used (when it hasn't). A new bug recently introduced?

It certainly should cause this error. color=rules means to read rules
from stdin, while rules=<filename> means to read rules from a named
file. If you specify both, where is it supposed to read the rules
from?

Arguably, the description for color=rules should have "from stdin"
appended to it, as that's how it behaves.

OK, I have submitted this patch:

~/grass64/lib/gis > svn diff colors.desc
Index: colors.desc

--- colors.desc (revision 33506)
+++ colors.desc (working copy)
@@ -21,7 +21,7 @@
rainbow: rainbow color table
ramp: color ramp
random: random color table
-rules: create new color table based on user-specified rules
+rules: create new color table based on user-specified rules read from stdin
ryb: red through yellow to blue
ryg: red through yellow to green
sepia: yellowish-brown through to white

Note that removing the mutual exclusivity check will simply cause the
rules= option to be ignored, as color= is checked first. The rules
option is only used if color= isn't given; specifically, the logic is:

       if <-i> read rules from stdin
       else if <color=...> handle the various color= choices
       else if <rules=...> read rules from the specified file
       else copy colours from another map (raster=)

FWIW, 7.0, doesn't accept color=rules; you need to use rules=- to read
rules from stdin (this makes it easier for the GUI, where reading from
stdin won't work.)

I have updated the docs of r.colors in both 6.4. and 7.trunk to reflect
their behaviours.

Markus