So this is curious: output to Cloud optimized Geotiff with ZSTD compression to
Level 17 is smaller than levels 18-22. Or at least that's my results when
testing compression results with Gdal 3.1 via Qgis 3.18 on Windows 10. I
expected compression levels to get smaller with higher levels, at expense of
longer and longer computation time. Levels 1 to 16 do that. Even more curious
than 17 being the smallest of the lot is that each step 18 to 22 is
progressively larger, albeit by a miniscule amount.
Here's my results:
% smaller than biggest Bytes Filename Compression Predictor
Level
24.2% 200,968,821 cog-zstd-pyes-lev17.tif zstd yes 17
22.8% 204,567,155 cog-zstd-pyes-lev18.tif zstd yes 18
22.8% 204,594,678
cog-zstd-pyes-lev19.tif zstd yes
19
22.8% 204,594,678 cog-zstd-pyes-lev20.tif zstd yes 20
22.8% 204,626,722 cog-zstd-pyes-lev21.tif zstd yes 21
22.8% 204,635,985 cog-zstd-pyes-lev22.tif zstd yes 22
22.6% 205,026,301 cog-zstd-pyes-lev16.tif zstd yes 16
21.5% 208,039,012
cog-zstd-pyes-lev15.tif zstd yes 15
21.5% 208,094,559 cog-zstd-pyes-lev13.tif zstd yes 13
21.5% 208,094,560 cog-zstd-pyes-lev14.tif zstd yes 14
21.3% 208,714,731 cog-zstd-pyes-lev12.tif zstd yes 12
21.2% 208,989,301 cog-zstd-pyes-lev11.tif zstd yes 11
21.2% 208,989,994 cog-zstd-pyes-lev10.tif zstd yes 10
21.1% 209,071,549 cog-zstd-pyes-lev9.tif zstd yes 9
21.0% 209,453,858 cog-zstd-pyes-lev8.tif zstd yes 8
20.9% 209,634,360 cog-zstd-pyes-lev7.tif zstd yes 7
20.7% 210,182,178 cog-zstd-pyes-lev6.tif zstd yes 6
20.4% 210,992,074 cog-zstd-pyes-lev5.tif zstd yes 5
18.9% 214,894,175 cog-zstd-pyes-lev4.tif zstd yes 4
17.4% 218,911,762 cog-zstd-pyes-lev3.tif lzw 2 3
16.6% 220,991,236 cog-dflt-p2.tif deflate 2
13.0% 230,553,902 cog-zstd-pyes-lev2.tif zstd yes
2
11.6% 234,277,147 cog-zstd-pyes-lev1.tif zstd yes 1
5.7% 249,979,858 cog-dflt-p1.tif deflate 1
0.0% 265,062,854 cog-lzw-p2.tif lzw 2
Command line pattern:
gdal_translate ^
-co compress=zstd ^
-co predictor=yes ^
-co level=3 ^
-co num_threads=all_cpus ^
-of cog ^
mtn-view.tif ^
mtn-view-cog-zstd-pyes-lev3.tif
Source image:
Name
AerialPhotos/AerialPhotos
URL
https://mapservices.gov.yk.ca/imagery/rest/services/AerialPhotos/AerialPhotos/ImageServer
Source
crs='EPSG:3578' format='JPGPNG' layer=''
url='https://mapservices.gov.yk.ca/imagery/rest/services/AerialPhotos/AerialPhotos/ImageServer'
CRS
EPSG:3578 - NAD83 / Yukon Albers - Projected
Export extent
Upper Left, Lower Left, Upper Right, Lower Right
356750.816, 702590.026
356750.816, 699097.526
361572.583, 702590.026
361572.583, 699097.526
Pixel size
0.5m
Do others see the same thing?
?Cheers,
Matt Wilkie
Environment | Information Management & Technology | 867-667-8133 ??
Yukon.ca<http://yukon.ca/>
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