Filed as https://github.com/OSGeo/gdal/issues/10174
Le 10/06/2024 à 10:57, Denis Rykov via gdal-dev a écrit :
Thank you, Jukka, for reproducing the behavior and explaining the
reason behind it!
On Mon, Jun 10, 2024 at 9:19 AM Rahkonen Jukka
<jukka.rahko...@maanmittauslaitos.fi> wrote:
Hi,
Those two commands behave in quite different ways. With “-oo
OVERVIEW_LEVEL=1” the output size is the size of the second
overview. In my test case the original has 12000 x 12000 pixels
and the command creates a 3000 x 3000 sized output
GDAL: GDALOverviewDataset(vrttest.vrt, this=000001CB3D728890)
creation.
GDAL: Using GTiff driver
GDAL: Computing area of interest: 26.8805, 63.2011, 27, 63.255
Creating output file that is 3000P x 3000L.
…
GDAL: GDALWarpKernel()::GWKNearestNoMasksOrDstDensityOnlyByte()
Src=0,0,3000x3000 Dst=0,0,3000x3000
...10...20...30...40...50...60...70...80...90...100 - done.
With -ovr 1 the output has the size of the full resolution image,
12000 x 12000 pixels, even the data is read from the 3000 x 3000
overview. The pixels will be upsampled.
GDAL: Using GTiff driver
GDAL: Computing area of interest: 26.8805, 63.2011, 27, 63.255
Creating output file that is 12000P x 12000L.
WARP: Selecting overview level 1 for vrttest.vrt
…
GDAL: GDALWarpKernel()::GWKNearestNoMasksOrDstDensityOnlyByte()
Src=0,0,1500x750 Dst=0,0,6000x3000
...10.GDAL:
GDALWarpKernel()::GWKNearestNoMasksOrDstDensityOnlyByte()
Src=1500,0,1500x750 Dst=6000,0,6000x3000
..20..GDAL:
GDALWarpKernel()::GWKNearestNoMasksOrDstDensityOnlyByte()
Src=0,750,1500x750 Dst=0,3000,6000x3000
.30...GDAL:
GDALWarpKernel()::GWKNearestNoMasksOrDstDensityOnlyByte()
Src=1500,750,1500x750 Dst=6000,3000,6000x3000
40...50GDAL:
GDALWarpKernel()::GWKNearestNoMasksOrDstDensityOnlyByte()
Src=0,1500,1500x750 Dst=0,6000,6000x3000
...60.GDAL:
GDALWarpKernel()::GWKNearestNoMasksOrDstDensityOnlyByte()
Src=1500,1500,1500x750 Dst=6000,6000,6000x3000
..70..GDAL:
GDALWarpKernel()::GWKNearestNoMasksOrDstDensityOnlyByte()
Src=0,2250,1500x750 Dst=0,9000,6000x3000
.80...GDAL:
GDALWarpKernel()::GWKNearestNoMasksOrDstDensityOnlyByte()
Src=1500,2250,1500x750 Dst=6000,9000,6000x3000
90...100 - done.
GDAL: Flushing dirty blocks:
0...10...20...30...40...50...60...70...80...90...100 - done.
The behavior is the same when using a TIFF with internal overviews
as input instead of VRT. Obviously the -ovr option has been
designed to force the use of some better-quality overview as
source data when warping yields a smaller, downsampled image. The
forced upsampling does not make much sense to me. I wonder if
gdalwarp should even allow that?
The gdal_translate utility has also -ovr option
https://gdal.org/programs/gdal_translate.html#cmdoption-gdal_translate-ovr.
It behaves in a different way when it comes to the size of the
output, but with gdal_translate it makes sense.
“When -ovr is specified to an integer value, and none of -outsize
and -tr is specified, the size of the overview will be used as the
output size.”
Maybe the thing to do is to improve the documentation of the
gdalwarp option
https://gdal.org/programs/gdalwarp.html#cmdoption-gdalwarp-ovr and
mention that this option does not have on effect on the size of
the output.
-Jukka Rahkonen-
*Lähettäjä:* gdal-dev <gdal-dev-boun...@lists.osgeo.org> *Puolesta
*Denis Rykov via gdal-dev
*Lähetetty:* maanantai 10. kesäkuuta 2024 2.27
*Vastaanottaja:* gdal dev <gdal-dev@lists.osgeo.org>
*Aihe:* [gdal-dev] Discrepancy in utilizing overviews with gdalwarp
I'd anticipate that both commands would yield the same outcome:
$ gdalwarp -oo OVERVIEW_LEVEL=1 -dstalpha input.vrt ovr1.tif
$ gdalwarp -ovr 1 -dstalpha input.vrt ovr1.tif
However, the reality is different. The first command behaves as
intended, utilizing overviews from |*.vrt.ovr|, while the second
command operates noticeably slower, seemingly disregarding the
overviews.
_______________________________________________
gdal-dev mailing list
gdal-dev@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/gdal-dev
--
http://www.spatialys.com
My software is free, but my time generally not.
_______________________________________________
gdal-dev mailing list
gdal-dev@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/gdal-dev
