[gdal-dev] Compression artifacts

[Even Rouault]

Le jeudi 27 décembre 2012 15:11:23, Jan Hartmann a écrit :
> On 12/27/2012 02:41 PM, Even Rouault wrote:
> > 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.
> > 
> >> OK Even, thanks. This means that I should use gdal-svn?
> > 
> > Not necessarily. I think you can workaround the issue by manually
> > building the overview on the .msk file as a post-processing step :
> > 
> > gdaladdo -ro --config COMPRESS_OVERVIEW DEFLATE small.tif.msk 2 4 8 16 32
> > 64
> 
> Do you mean I should use DEFLATE instead of JPEG as compression for
> overviews for the time being? What is the difference in compression ratio?

Use DEFLATE only for the mask file (see small.tif.msk in the above command 
line), as it is a lossless compression, which is needed for a mask. JPEG is 
fine for the imagery itself