[gdal-dev] resampling algs warp vs translate

[Even Rouault]

That should be relatively straightforward to adapt 
GDALResampleChunk_AverageOrRMS_T to do sum. Reuse the average code path, 
but just don't divide the sum by dfTotalWeight at lines 1418, 1473, 
1688, 1700 and 1712. And error out if applied to a band with a color 
table (cf line 4361)

For other algorithms, it could potentially be possible to re-use the 
warping code with an adaptation layer like done in 
GDALRasterBand::RasterIOResampled() in the bUseWarp case. Of course that 
would be less performant than implementing a specific overview 
resampling kernel which can assume that a source rectangle maps to a 
target rectangle at the band level, while the warping code only process 
pixel by pixel.

Le 21/09/2023 à 22:25, Michael Sumner via gdal-dev a écrit :
> Can we aspire to translate having the same set of resampling 
> algorithms as the warper?
>
> I see the warper adds min, max, mod, q1, q3, sum
>
> I especially wanted sum for OVERVIEW_RESAMPLING in COG, and I can see 
> where it's done and  ...  can maybe see my way through that ... but 
> the 600 lines of code in GDALResampleChunk_AverageOrRMS_T kind of 
> reins in my confidence.
>
> https://github.com/OSGeo/gdal/blob/26e7ff91504e0303434f440e6d19e58f2a206b45/gcore/overview.cpp#L1211C15-L1211C47
>
> It came up as a need for statistical properties required for 
> overview-publishers, and while I think we can incrementally build up 
> the SUM-pyramid with external overivews via CLI it would be awesome to 
> have the same stats for the two resampling regimes.
>
> Thank you
>
>
>
> -- 
> Michael Sumner
> Software and Database Engineer
> Australian Antarctic Division
> Hobart, Australia
> e-mail: mdsumner at gmail.com
>
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