[QGIS-trac] Re: [Quantum GIS] #1540: "Save as Image" georeference is off up to 1 cell

[Quantum GIS]

#1540: "Save as Image" georeference is off up to 1 cell
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        Reporter:  msieczka                                   |         Owner:  nobody       
            Type:  bug                                        |        Status:  new          
        Priority:  critical: causes crash or data corruption  |     Milestone:  Version 1.0.2
       Component:  Rasters                                    |       Version:  HEAD         
      Resolution:                                             |      Keywords:               
Platform_version:                                             |      Platform:  Debian       
        Must_fix:  Yes                                        |   Status_info:  0            
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Comment (by smizuno):

 Replying to [comment:2 mhugent]:

 I don't notice any offsets when I use the procedure you list. This is
 exactly what I was doing to determine the problem and test my changes. I
 have also tried at different scales - no difference between map and image.

 As long as the extent isn't changed the image saved exactly overlays the
 original map.

 I am using rasters in UTM zone 15, NAD83.

 I have considered what would happen with other CRS and believe that there
 shouldn't be any problem. I did test with a raster in a local county
 coordinate system in the same general area and found that the saved image
 exactly overlays the map as expected.

 Here are some Python statements I used to get the values for the world
 file, which I modified by hand at first. These were just executed in the
 Python console.
 The results should be the same as written to the world file for the saved
 image.

 Cell size:
 iface.mapCanvas().mapUnitsPerPixel()

 Coordinates of center of Upper Left cell:
 iface.mapCanvas().extent().xMinimum()+(iface.mapCanvas().mapUnitsPerPixel()/2),iface.mapCanvas().extent().yMaximum()-(iface.mapCanvas().mapUnitsPerPixel()/2)

 I am interested in any further information as I do want to get this
 correct.

 Regards, Steve

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Ticket URL: <https://trac.osgeo.org/qgis/ticket/1540#comment:3>
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