[mapguide-trac] #888: Reprojected raster gets blurring when view window crosses outside of original raster extents

[MapGuide Open Source]

#888: Reprojected raster gets blurring when view window crosses outside of
original raster extents
-------------------------------+--------------------------------------------
 Reporter:  stevenxu           |         Owner:  stevenxu
     Type:  defect             |        Status:  assigned
 Priority:  medium             |     Milestone:  2.1     
Component:  Rendering Service  |       Version:  2.0.1   
 Severity:  major              |    Resolution:          
 Keywords:  blurring           |   External_id:  1180334 
-------------------------------+--------------------------------------------
Changes (by stevenxu):

  * status:  new => assigned
  * owner:  StevenXu => stevenxu

Comment:

 This problem is cause by the  calculating precise error of double data
 type.
 When the MapGuide convers the maxium of WORLD-MERCATOR to LL84, it expect
 to get 180.0, but acctually it got the value 180.00000000000003 for it is
 double data type.
 Then this offset leads to the error of extent and eventually results in
 blurry image.

 \MgDev\OS\Common\CoordinateSystem\CoordSysTransform.cpp

 void CCoordinateSystemTransform::TransformPoint(double& x, double& y,
 double *pdZ)

 line 151:   nResult = CS_cs2ll(&m_src, dCoords, dCoords);
 This line code get the 180.00000000000003 value.

 line 189:  nResult = CS_ll2cs(&m_dst, dCoords, dCoords);
 This line change the 180.00000000000003 into -180, instead of 180.00.

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Ticket URL: <http://trac.osgeo.org/mapguide/ticket/888#comment:1>
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