[QGIS-trac] [Quantum GIS] #3127: support GRASS color rules

[Quantum GIS]

#3127: support GRASS color rules
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   Reporter:  hamish            |              Owner:  rugginoso    
       Type:  enhancement       |             Status:  new          
   Priority:  minor: annoyance  |          Milestone:  Version 1.6.0
  Component:  GRASS             |            Version:  Trunk        
   Keywords:                    |   Platform_version:               
   Platform:  All               |           Must_fix:  No           
Status_info:  0                 |  
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 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

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Ticket URL: <https://trac.osgeo.org/qgis/ticket/3127>
Quantum GIS <http://qgis.org>
Quantum GIS is an Open Source GIS viewer/editor supporting OGR, PostGIS, and GRASS formats