[gdal-dev] Feature request: gauss and other interpolations in gdalwarp

[Even Rouault]

Le mardi 09 avril 2013 19:06:28, Etienne Tourigny a écrit :
> I have committed new warping methods average and mode to trunk, this will
> be part of gdal-1.10

Hi Etienne,

It would be good if you could extend the autotest suite to add tests for those 
new warping methods. For that, you can likely take inspiration from the first 
tests of autotest/warp/warp.py. "Reference" images based on utmsmall.tif 
reference image is a bit big, but you can likely start from a smaller source 
image like byte.tif instead that will produce reference images of reasonable 
size to be put in svn.

Regarding nAlgo == 2 (mode with foating point data), the allocations of 
pafVals and panSums have the potential to fail if warping is done on a large 
image whose floating point values are rarely identical. So I think that 
VSIRealloc shoud be used instead with a test on the result to fail properly. 
I'm also a bit doubtfull about the practical usefulness of this case on real 
data. There might also be a performance issue due to the loop "//Check array 
for existing entry" that is at the most inner level of the algorithm. Unless 
you have a practical use case, my personnal opinion would be to refuse to run 
mode resampling on floating point data, or implement it with a tolerance 
parameter to avoid strict floating point comparison (if that makes sense), but 
even that wouldn't guarantee reasonable performance and memory consumption.

As far as mode resampling is concerned, it would likely run correctly for 
images with color tables, so I believe that the warning in gdalwarp.cpp at 
line 1048 could be shut down in that case too (in addition to nearest 
resampling)


Best regards,

Even