On 2/12/2017 9:54 AM, Even Rouault wrote:
On samedi 11 février 2017 18:18:35 CET Stephen Woodbridge wrote:
Hi All,
I need your wisdom. I'm downloading NAIP DOQQs in GTiff format and I
have a processing chain something like the following:
gdalwarp -t_srs EPSG:4326 -dstalpha -r "bilinear -multi -co TILED=YES
-dstnodata '0 0 0' srctiff tmpfile
nearblack -nb 15 -q tmpfile
gdal_translate -co TILED=YES -co JPEG_QUALITY=90 -co COMPRESS=JPEG -co
PHOTOMETRIC=YCBCR -b 1 -b 2 -b 3 -mask auto --config
GDAL_TIFF_INTERNAL_MASK YES tmpfile, target
nearblack -nb 5 -q target
gdaladdo -clean -r bilinear target 2 4 8 16 32 64 128 512
And create a tileindex for mapserver of all the tiffs
If I skip the gdal_translate (ie: JPEG compression) and the 2nd
nearblack, the doqq tiles are perfect with no nearblack edges between
the doqq tiles. But when a JPEG compress them, I get edges between the
doqqs like this:
http://imaptools.com:8080/dl/doqq-issue.jpg
I've never used the JPEG in tiff compression and I'm very impressed by
the amount of size reduction there and how good the image remains, but I
have not been able to figure out the magic trick to clearing the edge
artifacts.
Steve,
I managed to replicate something similar to the above with an image I've
at hand.
The cause of the issue is the nearblack invokation after the
gdal_translate. The effect of this nearblack is to "eat" some pixels at
the border of the validity / invalidity transition, but that doesn't
update the existing mask.
If you add -setmask to this nearblack, that should fix it.
Even better, I think you can just remove this second nearblack.
And you probably must add -setalpha for the first nearblack invokation
as well.
Even,
Thanks for the quick feedback. I'll will give these suggestions and try
today and let you know how it goes.
Thanks,
-Steve
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