Opened 11 years ago

Last modified 11 years ago

#3127 new enhancement

support GRASS color rules

Reported by: hamish Owned by: rugginoso
Priority: minor: annoyance Milestone: Version 1.7.0
Component: GRASS Version: Trunk
Keywords: Cc: neteler
Must Fix for Release: No Platform: All
Platform Version: Awaiting user input: no


I see qgis has just got some better graduated symbol/color improvements, great! that's been lacking for a long time. Compared to that GRASS's r.colors and v.colors modules are so much more powerful, so until qgis has better raster+vector color support I'd like to set those in GRASS and have QGIS be able to read the color rules from GRASS exported geotiffs and shapefiles. (the people I deliver maps to often run qgis but not grass)

vector: (mostly shapefiles)

  • it would be great if the point icon's or line's color could be read from

an attribute column containing a R:G:B string (0-255). In GRASS see d.vect + GRASSRGB column (but the column can be called anything). that way you could use v.colors (qgis grass toolbox) to set more powerful color gradients.

  • When a GeoTiff? is exported from GRASS with r.out.gdal, the first 1000

lines of the color rules file (usually there is less than 10) is written to the GeoTiff? metadata as "COLOR_TABLE_RULE_RGB_n" where "n" starts at 1 and goes up. the rest of the line looks like:

min max R1 G1 B1 R2 G2 B2

with RGB values for the min and max within that range. colors for values in between that step are linearly interpolated between R1,R2 etc. Also the new GDAL version seems to be making filename.tif.aux.xml too, which contains those COLOR_TABLE_RULE_RGB_1,2,3,... rules.

the long term idea would be for many OSGeo projects to share a common color formats for these things, so data can be more easily shared. (for what it's worth, GMT and GRASS already are very similar for some things like this, I think it has to do with common code ancestry 15+ years ago, and partly ending up with common solutions after years of trying different methods)

(working on a common .svg icon/symbol pool is another idea along these lines.)

thanks, Hamish

Change History (2)

comment:1 Changed 11 years ago by neteler

Cc: neteler added

comment:2 Changed 11 years ago by neteler

See also #782

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