Le 31/12/2021 à 09:04, Evert Etienne (SITEMARK) a écrit :
> If you output to regular GTiff, the 2 step process might be needed
to get the best compression
Are there some guidelines to when this is needed since you say 'might'?
Would it be possible to explain why this is the case?
By default, warping doesn't proceed by chunks that would necessarily
align on entire target blocks, so some target blocks might be rewritten
several times, which will usually cause some space to be lost in the
file if it uses compression (at least this is true for GeoTIFF output).
The whole logic is at
https://github.com/OSGeo/gdal/blob/master/alg/gdalwarpoperation.cpp#L1363.
The -wo OPTIMIZE_SIZE=YES warping option can be specified to avoid that,
but it is sometimes detrimental for speed of execution if the shapes of
the source and target images are significantly different due to
characteristics of their CRS.
Thanks
On Dec 30, 2021 23:26, Even Rouault <[email protected]> wrote:
Matt,
There has been an enhancement in gdalwarp to support writing
directly to drivers, like COG, that supports only the CreateCopy
mode. So you don't need the 2 step process and can directly
gdalwarp -of COG (it will more or less do the 2 steps internally)
If you output to regular GTiff, the 2 step process might be needed
to get the best compression
Even
Le 30/12/2021 à 22:29, [email protected]
<mailto:[email protected]> a écrit :
A few years ago it was best practice to follow a gdal warp
process with translate in order to get better compression, and
even overall speed although extra disk write is involved. Is
this still the case? and when using COG output driver? e.g.
gdalwarp infile.tif interim.tif
gdal_translate -of cog -co compress=zstd interim.tif final.tif
thanks!
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