[GRASSLIST:1047] Re: patched rasters

[Glynn Clements]

Maciek Sieczka wrote:

> > An alternative approach would have been to start by using a graphics
> > package to give all the source images the same colour palette.
> 
> Could you explain how to do it or point to a good source?

In GIMP (2.2.11):

1. Image -> Mode -> RGB
2. Image -> Mode -> Indexed ...
3.
 a) choose "Use custom palette" option
 b) select a palette
 c) uncheck "Remove unused colors from final palette"
 d) select a dithering mode appropriate to the data (if you want to
    preserve contiguous regions, use None)
4. click OK

Repeat for each image, using the same palette for each.

If none of the standard palettes are suitable, before converting the
first image to RGB, do:

1. Dialogs -> Palettes
2. Right click in the palette dialog
3. Import palette ...
4. choose Image
5. click Import

For command-line usage, use ImageMagick's "convert" program with the
-map and +map options.

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