[GRASS-dev] [GRASS GIS] #3210: r.texture: bug when non continuous series of values

[GRASS GIS]

#3210: r.texture: bug when non continuous series of values
--------------------------+-------------------------
  Reporter:  mlennert     |      Owner:  grass-dev@…
      Type:  defect       |     Status:  new
  Priority:  normal       |  Milestone:  7.2.0
 Component:  Raster       |    Version:  svn-trunk
Resolution:               |   Keywords:  r.texture
       CPU:  Unspecified  |   Platform:  Unspecified
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Comment (by mlennert):

 Replying to [comment:3 mlennert]:
 > Just one question:
 >
 >
 > The manual says:
 >
 > r.texture  assumes  grey levels ranging from 0 to 255 as input.  The
 input is automatically rescaled to 0 to 255 if the input map
 >        range is outside of this range.
 >
 >
 > But when I rescale the above (second) matrix to 0,255 I get a different
 result:
 >
 >
 > {{{
 > r.in.ascii --o in=- out=test_matrix <<EOF
 > north: 3
 > south: 0
 > east: 3
 > west: 0
 > rows: 3
 > cols: 3
 > 1 1 1
 > 3 0 0
 > 0 0 3
 > EOF
 > r.texture -s test_matrix out=text method=idm --o
 > r.stats -1n text_IDM_90
 > 0.40000007
 >
 > r.rescale test_matrix out=test_matrix_rescaled to=0,255
 > r.texture -s test_matrix_rescaled out=text_rescaled method=idm --o
 > r.stats -1n text_rescaled_IDM_90
 > 0.16672371
 > }}}
 >
 > I would have thought that the result should be the same ?

 I see this comes from lines 277ff in main.c:

 {{{
     inscale = 0;
     if (min < 0 || max > 255) {
         inscale = 255. / (max - min);
     }
     /* input has 0 - 1 range */
     else if (max <= 1.) {
         inscale = 255. / (max - min);
     }
 }}}

 So, as long as the data does not contain a value above 255 we just assume
 that it is scaled to 255, unless the max is < 1.

 So, data with 0, 1, 2, 3 is just considered as already being scaled to
 0,255...

 Don't know, yet, what to think of this.

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Ticket URL: <https://trac.osgeo.org/grass/ticket/3210#comment:4>
GRASS GIS <https://grass.osgeo.org>