[QGIS-trac] [Quantum GIS] #3340: Raster clipper: shifted results

[Quantum GIS]

#3340: Raster clipper: shifted results
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   Reporter:  alobo                             |              Owner:  nobody       
       Type:  bug                               |             Status:  new          
   Priority:  major: does not work as expected  |          Milestone:  Version 1.7.0
  Component:  Rasters                           |            Version:               
   Keywords:                                    |   Platform_version:               
   Platform:  All                               |           Must_fix:  No           
Status_info:  0                                 |  
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 I think the way the area to be clipped is set in raster/clipper is wrong.
 Currently, for results to be correct, the area to be clipped must be
 coincident with pixel boundaries. In other
 words, the 4 corners must be pixel corners.
 If the corners of the defined area are within the pixel, the result is
 shifted, as it is not interpolated.

 I think that if no interpolation is the goal, then the coordinates
 entered by the user should be moved to the closest
 pixel corners, and the user be warned. Then the clipping would be exact.

 If floating clipping is the goal, then the user must enter the
 resolution of the new raster and interpolation must
 be performed.

 Obviously having the option would be the best, but as the second
 option is more complicated, having the first one
 implemented first would make a lot of sense.

 I've put a zipped file with a qgis project and layers to illustrate
 the problem here:

 https://sites.google.com/site/filestemp2/home/clip_problem.zip

 Agus

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Ticket URL: <https://trac.osgeo.org/qgis/ticket/3340>
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