[gdal-dev] MBTiles blurry

[Even Rouault]

You can perhaps try -r lanczos . It is good at preserving sharp details 
(but can also create artifacts on other situations. there's nothing as a 
universally good resampling method)

Ah, and one point I forgot is that when going to MBTiles, an implicit 
reprojection to Web Mercator is also done by the MBTiles driver, which 
involves another resampling

Try also adding -co RESAMPLING=LANCZOS in the gdal_translate stage.

If you don't need MBTiles format and WebMercator projection, I'd say 
just stick with GeoTIFF, and possibly use the COG driver: 
https://gdal.org/drivers/raster/cog.html

Le 30/06/2022 à 13:18, Kanishk Varshney a écrit :
> Hey Even,
> Thanks for the quick response.
>
> If you notice the MBTiles, the finer details(cracks on Road, etc) and 
> edges are all blurred. I tried the -r average flag as well but the 
> result was almost similar
>
> I am more interested in preserving those details while reducing the 
> size of the data. So any other approach or format that might suit my 
> use case will be appreciated as well!
>
> Thanks,
> Kanishk
>
> On Thu, Jun 30, 2022 at 3:37 PM Even Rouault 
> <even.rouault at spatialys.com> wrote:
>
>     Kanishk,
>
>
>>
>>     And my GDAL commands are:
>>
>>     gdalwarp -srcnodata 0 -dstalpha infile.tif outfile.tif
>>     gdal_translate -tr 0.035 0.035 -co 'QUALITY=100' -of MBTILES
>>     outfile.tifoutmbtile.mbtiles
>>     gdaladdo -r nearest outmbtile.mbtiles2 4 8 16
>
>     The above gives a OK result for me with topveiw_sample.tif as
>     input. Note that you don't need the first gdalwarp step as your
>     file has already an alpha band.
>
>     To improve quality you should add for example -r average to
>     gdal_translate otherwise nearest neighbour reampling will be used,
>     which is generally a bad idea.
>
>     Same for gdaladdo: you should'nt use nearest neighbour reampling
>     for good quality
>
>>     If I am trying to improve the target resolution even further(reducing -tr value) , it corrupts the output mbtile and a blank or blurred tile gets generated
>>     Also, the opening option ZOOM_LEVEL seems to error out(Using with -oo "ZOOM_LEVEL=9)
>
>     If you look at the output of gdalinfo on the generated mbtiles
>     file, you'll see that the full resolution is at zoom level 22, and
>     given the dimensions of the file only 2 overview levels were
>     generated. So the minimum zoom level at which you can open that
>     file is 20.
>
>     Even
>
>     -- 
>     http://www.spatialys.com
>     My software is free, but my time generally not.
>
-- 
http://www.spatialys.com
My software is free, but my time generally not.
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