aerial photo mosaic
malcolm at cast.uark.edu
Fri Aug 15 09:54:41 EDT 1997
On Fri, 15 Aug 1997, Simon Cox wrote:
> Joe - r.patch messes with the color table in an
> attempt to maintain the appearance of the output.
> It treats the raster's as category maps, rather than
> continuous fields, so pixels with similar values do
> *not* get assigned similar colors.
> However, since the GRASS display colour-space is
> restricted to 216 colours, this usually fails for
> rasters with a large number of categories, such as images.
> Images are a particular problem, of course, since adjacent
> scenes frequently have different average levels, so features
> which any intelligent observer would interpret as continuous
> across the join will be really messed up. Mosaicing
> remote-sending images successfully is a long-standing
> problem. If you intend to do quantitative analysis you
> more-or-less have to do it one frame at a time.
> If you just want somthing that looks OK, than try manipulating
> the color look-up-table, either manually by editing
> or by using r.colors
> (NB d.colors only changes the display so
> does not persist between sessions).
Let me expand on the above statement - d.colors _does_ permanently affect
your colortable _if_ you use the "save color table" (the "c" key) option.
I've been using it for years to edit my color table.
> Dr Simon Cox - Australian Geodynamics Cooperative Research Centre
> CSIRO Exploration & Mining, PO Box 437, Nedlands, WA 6009 Australia
> T: +61 8 9389 8421 F: +61 8 9389 1906 Simon.Cox at dem.csiro.au
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