[GRASS-dev] Re: [GRASS GIS] #73: r.out.gdal tiff output does not work

Wed Apr 15 07:16:43 EDT 2009

#73: r.out.gdal tiff output does not work
--------------------------+-------------------------------------------------
  Reporter:  helena       |       Owner:  grass-dev at lists.osgeo.org
      Type:  defect       |      Status:  new                      
  Priority:  critical     |   Milestone:  6.4.0                    
 Component:  Raster       |     Version:  svn-trunk                
Resolution:               |    Keywords:  r.out.gdal, tiff         
  Platform:  Unspecified  |         Cpu:  Unspecified              
--------------------------+-------------------------------------------------
Comment (by hamish):

 This was and is my main concern. MarkusM's patch could address this, I
 haven't run exaustive tests so don't know.

 Replying to [comment:20 hamish]:
 >  - oops, you are quite right. nodata must be set to something valid,
 otherwise the module doesn't know how to write out NULL values when  it
 comes to them. It can't just skip them and nan is not an option for int
 maps. Thus, as you proposed, in the case where nodata= is out of range for
 the data type the module should exit with an error.
 > I was just thinking of what to do for the metadata tag; not how the
 module would deal with NULL values.
 >
 >  - if a Byte map has data 0-255 *and* NULL, it seems reasonable to me to
 default to nodata=255 + issue a warning. *But* if a map has 0-255 with
 *no* NULLs, nodata should not be set* to 255, as this would lead to a loss
 of fidelity. (improper removal of all cells with cat=255 for no gain)
 >
 > [*] ie should not be set, unless the user requests it explicitly with
 the nodata= opt
 >
 >
 > sorry to be so thick,
 > Hamish

 As for the other matter, I'm not worried if other software do not respect
 the GeoTiff spec, as long as we do. (it's all we have control over anyway)