Tim wrote: > I am trying to patch together a number of 1 km by 1 km tiles of a map > whose values are either 0 or 1 (black on white background). > > If I use r.patch to put 2 tiles together is appears to work fine but > if however I try and patch more, even if it is two tiles of already > patched tiles I get one set when patched as black background and > white features and the other part as white background and black > features. It appears that the second in the case of already patched > data or third and subsequent in case of more than 2 tiles is inverted > with 1 becoming 0 and 0 becoming 1. > > I have tried reducing region to the smallest. Maps are at 0.2m > resolution. I am hoping to get a 5 tile by 5 tile block > > I have tried this across two different platforms (Mac OS and OpenSuse > ) on the latest downloadable binary versions of GRASS. > > Am I doing something wrong?
I suspect that the images are paletted, and the color palettes differ between the images. After confirming that you might run the images through a bulk color palette -> 24bit RGB filter. (I'm not sure what the right NetPBM or ImageMagick command is, but I'm sure there is one) after that, gdalbuildvrt is wonderful for import + patch in one step. good luck, -- Hamish <[email protected]> _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
