[GRASS-dev] Re: [GRASS GIS] #1071: histogram equalized color rules for raster takes inordinately long to display

[GRASS GIS]

#1071: histogram equalized color rules for raster takes inordinately long to
display
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  Reporter:  isaacullah  |       Owner:  grass-dev at lists.osgeo.org                
      Type:  defect      |      Status:  new                                      
  Priority:  major       |   Milestone:  6.4.0                                    
 Component:  Display     |     Version:  6.4.0 RCs                                
Resolution:              |    Keywords:  histogram equalization, display, r.colors
  Platform:  Linux       |         Cpu:  Unspecified                              
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Comment (by glynn):

 Replying to [ticket:1071 isaacullah]:
 > Recently, I have discovered that displaying a map that has been
 recolored using the histogram equalization option (-e) in r.color takes
 much much much longer than displaying the same map colored without the
 histogram equalization option. With a histogram equalized raster, every
 redisplay takes about 5 minutes,

 If you use -e on an integer map, it will create one rule for each value
 which occurs in the map, which can result in an excessively large colour
 table.

 I'm sure that this very issue has been addressed before, but I don't
 remember the details.

 The quick fix would be to use the same code as for floating point (which
 just splits the range into 1000 bins, and always generates 1000 rules). A
 better fix is to coalesce a run with a constant colour into a single rule.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1071#comment:1>
GRASS GIS <http://grass.osgeo.org>