[Scipy-tickets] [SciPy] #515: ndimage.zoom introduces artefacts at right and bottom edges

SciPy scipy-tickets@scipy....
Wed Oct 17 19:42:36 CDT 2007


#515: ndimage.zoom introduces artefacts at right and bottom edges
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 Reporter:  0ion9                                  |        Owner:  stefan  
     Type:  defect                                 |       Status:  assigned
 Priority:  normal                                 |    Milestone:  0.7     
Component:  scipy.ndimage                          |      Version:  devel   
 Severity:  normal                                 |   Resolution:          
 Keywords:  ndimage, data, representation, spline  |  
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Comment (by stefan):

 Another point: why can't mirror extension work?  Remember that we can
 interpolate a value inside our data, i.e. any coordinate from 0 to L-1,
 where L is the length of the array.  If we extend by reflection, we have
 coefficients:

 0, 1, 2, 1, 0

 We can interpolate anywhere between (0,1),(1,2),(2,1),(1,0).  But if we
 extend by mirroring, we have

 0, 1, 2, 2, 1, 0

 We cannot interpolate between (2,2) -- that spline fit is never done.  To
 do that, the interpolation algorithm will have to be modified to *first*
 extend the series, then do a spline fit, etc.  (Currently, interpolation
 requires no extension before fitting splines).

-- 
Ticket URL: <http://scipy.org/scipy/scipy/ticket/515#comment:3>
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