Opened 12 years ago

Closed 12 years ago

#1951 closed defect (fixed)

Lanczos Resample Anomolies near nodata values.

Reported by: warmerdam Owned by: dron
Priority: normal Milestone: 1.5.2
Component: Utilities Version: svn-trunk
Severity: normal Keywords: gdalwarp lanczos
Cc:

Description

Andrey,

When I run the following warps, I see a trough in the pixels values along the left side of the valid data in the lanczos result, but nothing like that in the cubic spline output. I think this is a problem in the lanc resampler but I'm not positive. Could you look into it at some point? Let me know if you need me to more specifically highlight the issue.

gdalwarp warpsamp.tif -tr 500 500 -rcs out.tif -srcnodata -32768
gdalwarp warpsamp.tif -tr 500 500 -r lanczos  out.tif -srcnodata -32768

Attachments (1)

warpsamp.tif (20.0 KB) - added by warmerdam 12 years ago.
input file to demonstrate lanc issue.

Download all attachments as: .zip

Change History (2)

Changed 12 years ago by warmerdam

Attachment: warpsamp.tif added

input file to demonstrate lanc issue.

comment:1 Changed 12 years ago by Even Rouault

Milestone: 1.5.11.5.2
Resolution: fixed
Status: newclosed

The problem was that dfAccumulatorWeight can be > 1 when we ignore some source nodata values, and the normalization of values and densities was only done when dfAccumulatorWeight < 1.

I think this could also happen in cubic spline resampling so I fixed both.

Fixed in trunk in r14126 and in branches/1.5 in r14127.

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