[gdal-dev] Compression artifacts

[Jan Hartmann]

On 12/27/2012 02:27 PM, Even Rouault wrote:
> The artifacts are due to the lossy characteristics of JPEG compression that
> are particularly visible on borders between nodata pixel and valid pixels. An
> option would be to use nearblack to create a .msk mask file :
>
> nearblack -setmask -o big_with_mask.tif big.tif -of gtiff
>
> (I'm not sure if your original image has black or white nodata areas. If it is
> white, then add -white to the previous command line)
>
> And then do the gdal_translate with big_with_mask.tif as input (you should
> perhaps consider adding "-co TILED=YES" too), and then gdaladdo. I've just
> pushed a fix since building overviews with "--config COMPRESS_OVERVIEW JPEG --
> config PHOTOMETRIC_OVERVIEW
> YCBCR" when there's a .msk didn't work.
>
> MapServer should be able to use the mask file as a transparency mask.
>
>
OK Even, thanks. This means that I should use gdal-svn?
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