[GRASS-dev] Re: [GRASS GIS] #774: i.rgb.his, i.his.rgb, d.his support for >8 bit

GRASS GIS trac at osgeo.org
Mon Oct 5 20:39:59 EDT 2009

#774: i.rgb.his, i.his.rgb, d.his support for >8 bit
  Reporter:  hamish       |       Owner:  grass-dev at lists.osgeo.org  
      Type:  enhancement  |      Status:  new                        
  Priority:  normal       |   Milestone:  6.5.0                      
 Component:  Raster       |     Version:  svn-develbranch6           
Resolution:               |    Keywords:  i.rgb.his, i.his.rgb, d.his
  Platform:  All          |         Cpu:  All                        
Comment (by glynn):

 Replying to [ticket:774 hamish]:

 > it would be nice if i.rgb.his, i.his.rgb, d.his modules could have
 support for >8 bit colors.

 > i.his.rgb and d.his are a bit deeper into the max=255 and casting CELLs
 to unsigned char.

 d.his uses the raster's colour table, so it will work with integer rasters
 of any bit depth, as well as FP rasters. The use of 8 bits within d.his is
 due to both GRASS' colour tables and the display architecture using 8-bit
 intensity values.

 I'm not sure that there is much point in changing the display architecture
 when display hardware which supports more than 8-bit intensity is so rare
 (I know that some image formats support more than this, but that's not
 much use if the images are going to be displayed on hardware which only
 supports 8 bits).

 For i.* or r.* modules, you can either use the raster's colour table, or
 you need an associated scale parameter for each input raster (and possibly
 an offset parameter as well), or you require that all inputs be FP rasters
 where 0.0 is black and 1.0 is white.

 Using the colour table limits you to 8-bit resolution, but it does at
 least allow you to use maps with more resolution as inputs.

Ticket URL: <https://trac.osgeo.org/grass/ticket/774#comment:2>
GRASS GIS <http://grass.osgeo.org>

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