[gdal-dev] Problem with black edges to DOQQs using JPEG in Tiff compression

Stephen Woodbridge woodbri at swoodbridge.com
Sun Feb 12 10:46:00 PST 2017


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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