Hello List, I am trying to generate PNG files of a few different maps using r.colors, d.rast, and the PNG driver.
The images I get from this process end up being colored slightly differently than when the equivalent images are generated in QGIS. It is far more convenient to use the PNG driver right in GRASS (because I can set a script running and print out many images at once), but I prefer the color results I get with QGIS. In GRASS, I am using r.colors map=ForestChange rules=colorTable.file d.mon start=PNG d.rast map=ForestChange d.mon stop=PNG with the rules file (colorTable.file) as follows using the rgb values for each level: -15 255 0 0 -0.5 255 240 180 0 white 0.5 180 230 130 15 0 70 0 (the idea with this particular rules file is to generate deforestation / reforestation maps where zero change is shown as white, with beige-red representing increasing levels of deforestation, and light green - dark green representing increasing levels of reforestation). Then, I take the same raster file (ForestChange), load it in QGIS, and set its colormap according to what I think are the same rules: http://i1020.photobucket.com/albums/af326/timothyholland/QGIScolorTable.jpg The two resulting files don't look the same, however. The GRASS PNG output has a far more yellow-ish tone. I think the QGIS one is quite a bit nicer. GRASS: http://i1020.photobucket.com/albums/af326/timothyholland/GRASS_PNG_map.jpg QGIS: http://i1020.photobucket.com/albums/af326/timothyholland/QGISmap.jpg. I have tried the various flags in the r.colors module (-g / Logarithmic scaling; -e / Histogram equalization; and the default), but all seem to return a similar result to the image which is given here). As a test, I also took a landsat composite image that I had generated using r.composite. In this case, the color table was set by r.composite without any input from me, so I was really expecting the same output. However, again, the QGIS output has much more natural-seeming colors. GRASS: http://i1020.photobucket.com/albums/af326/timothyholland/HLB_brovey_GRASS.jpg QGIS: http://i1020.photobucket.com/albums/af326/timothyholland/HLB_brovey_QGIS.jpg. Does anyone know if there is a way to better approximate the QGIS color results using GRASS directly? According to the QGIS GUI, color interpolation (for the forest maps, at least) is linear, which should be the most straightforward interpolation, shouldn't it? Thanks for any help / advice anyone can provide. Best, Tim -- View this message in context: http://n2.nabble.com/r-colors-generates-different-colors-than-QGIS-plugin-when-same-rules-used-tp3558680p3558680.html Sent from the Grass - Users mailing list archive at Nabble.com. _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
