[gdal-dev] gdalwarp vs gdal_translate for scaling

[Michael Sumner]

in short, warp will give you exactly the target extent of a (possibly) new
grid specification in that -te subdivided by the -ts.

translate will give you approximately the extent provided to projwin, but
snapped to the source grid alignment at a particular zoom implied by the
projwin subdivided by the outsize.

Further, translate can do scaling but warp cannot, which I guess is why you
have a vrt in the workflow - you can scale a source virtually with
translate to vrt, then warp (or translate) that.

(Finally it's a bit sloppy to have such arbitrary extent values that warp
will preserve and I routinely snap them to the source alignment, and I'm
interested to provide such a feature in the warper options too.)

Hope that helps!






On Fri, 6 Jan 2023, 03:16 Daniel Mannarino, <daniel.mannarino at gmail.com>
wrote:

> Hi folks!
>
>
>
> We have a process that generates web mercator zoom levels by resampling
> from the next higher up, from the original resolution down to zoom level 0.
> Currently we do so with gdalwarp, but a team member realized that
> gdal_translate is capable of the same, and at first glance is much faster.
> Unfortunately, using the two commands (below) which I intended to do
> exactly the same thing winds up with slightly different results (can/should
> I post a small image here to illustrate?).
>
> I won't ask "Which is correct?" because the answer is almost certainly
> "That depends on what you want". But can someone help me understand the
> difference between what is done with the gdalwarp command versus the
> gdal_translate one so that I can decide if using gdal_translate is an
> acceptable solution? Here are the two commands:
>
>
>
> gdalwarp -te 12523442.714243278 0.0 15028131.257091936 2504688.5428798534
> -ts 65536 65536 -r mode -co TILED=YES ../source_tiles/everything.vrt
> 007R_013C_warp_mode.tif
>
>
>
> gdal_translate -r mode -projwin 12523442.714243278 2504688.5428798534
> 15028131.257091936 0.0 -outsize 65536 65536 -co TILED=YES
> ../source_tiles/everything.vrt 007R_013C_translate_mode.tif
>
>
>
> Thank you!
>
> Daniel Mannarino
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