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

[GRASS GIS]

#73: r.out.gdal tiff output does not work
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  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              
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Comment (by hamish):

 These messages get a bit long so I'll reply in full in the next message.

 But quickly-

  - 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

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Ticket URL: <https://trac.osgeo.org/grass/ticket/73#comment:20>
GRASS GIS <http://grass.osgeo.org>