[GRASS-dev] Re: [GRASS GIS] #967: r.out.png: respect TRANSPARENT and COMPRESSION enviro vars

[GRASS GIS]

#967: r.out.png: respect TRANSPARENT and COMPRESSION enviro vars
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  Reporter:  hamish       |       Owner:  grass-dev at lists.osgeo.org
      Type:  enhancement  |      Status:  new                      
  Priority:  normal       |   Milestone:  7.0.0                    
 Component:  Raster       |     Version:  svn-trunk                
Resolution:               |    Keywords:  r.out.png                
  Platform:  All          |         Cpu:  All                      
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Comment (by glynn):

 Replying to [comment:6 hamish]:

 > > png_set_bKGD()
 >
 > changed to use that in r41241, but I'm still getting a segfault.
 confused by the layers of structs and `^usage`.

 The (pointer) variable isn't being initialised. Use a structure and pass
 its address:
 {{{
         png_color_16 background_color;
         background_color.red = (png_uint_16)def_red;
         background_color.green = (png_uint_16)def_grn;
         background_color.blue = (png_uint_16)def_blu;
         png_set_bKGD(png_ptr, info_ptr, &background_color);
 }}}

 > ps- what does r.in.png do which r.in.gdal doesn't?

 Provides more options, e.g. gamma correction, conversion to float. Also,
 by default it imports the raw values rather than expanding to bytes.

 > is PNG a flexible enough format to help with the 6-7 raster format
 transition | grass-gdal driver plugin | r.external ?

 No, it's limited to 16-bit integers.

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Ticket URL: <https://trac.osgeo.org/grass/ticket/967#comment:7>
GRASS GIS <http://grass.osgeo.org>