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

[Brian Case]

Steve,

first, if your data is non lossy you need to nearblack -nb 0 -near 15

however your DOQQ's dont have a collar so there is no reason to
nearblack

gdalwarp -dstalpha will crate an alpha band to mask out the collar after
gdalwarp rotates the image. no nead to nearblack the output of gdal
warp.

when using gdal_translate to create a tiff with a mask band, and you
warped file has a alpha band, gdal_translate -b 1 -b 2 -b 3 -mask 4
this will crate a mask band from the alpha band

brian

On Sat, 2017-02-11 at 18:18 -0500, 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.
> 
> Any help would be appreciated.
> 
> Thanks,
>    -Steve
> 
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