On Thu, Mar 22, 2012 at 09:03, Rahkonen Jukka <jukka.rahko...@mmmtike.fi> wrote: > Stephen Woodbridge wrote: > >> On 3/21/2012 11:18 PM, Ian Walberg wrote: >> > Folks, >> > >> > We are using tif format images and getting good map rendering >> > performance. >> > >> > However the image file size could do with reducing a little. >> > >> > Anyone got experience of what compression options we have >> that have the >> > least impact on performance? >> >> My experience of working with USGS DOQQ satellite imagery in GeoTiff >> files, was that the amount of compression really did not make a >> significant reduction in size. We used internally tiled tiff >> files with >> overviews and had over 15TB of imagery online. There are >> other formats >> that provide higher compression rates like MrSID and others, but >> depending on the format the behavior characteristics vary >> greatly and I >> do not have any recent stats or comparisons of size versus >> performance >> versus format. > > > Hi, > > I took numbers from one of our orthoimage set > > Uncompressed tiff files from the contractor > 667 File(s) 289 260 585 944 bytes > > What we have on server disk after running > gdal_translate -co COMPRESS=JPEG -co PHOTOMETRIC=YCBCR > 667 File(s) 21 411 672 702 bytes
I suspect you'll get superior access performance if you add -co TILED=yes to that command (and to your gdaladdo overview creation also). >From my experience, tiled tiffs with jpeg compression and overviews was by far the best compromise between disk usage and access performance, provided the jpeg destructive compression isn't a showstopper for your particular application. -- thomas > > Reduction in size 93%. Aerial images are used for on-screen interpretation > and difference in quality is not visible with bare eyes. The rate of the JPEG > compression can be adjusted but I have been happy with GDAL defaults. > Overviews seem to add about 40-50% to JPEG compressed images. Those I have > created probably as > gdaladdo -ro --config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW > YCBCR > --config INTERLEAVE_OVERVIEW PIXEL tiff.tif 2 4 8 16 32 64 > > We have also JPEG2000 versions of the images but GDAL does not handle them as > fast as JPEG-in-TIFF files. A few years ago the speed with JPEG2000 (with > EWCJP2 and KAKJP2 drivers) was about the half of what we got with tiffs. > Those numbers are nothing to rely on today because the software versions have > changed so many times. Because of the unfriendly licenses of the good > JPEG2000 libraries and because jpeg-in-tiff works so well I have not bothered > to repeat the tests myself lately. Generally, for this kind of questions the > best answer is achieved by making a well controlled test in your own > environment. You can then publish your results and tell how you did the test > so that others can check if something has been were poorly configured. For > example it is not at all the same how JPEG2000 images have been compressed > and JPEG compressed tiffs without tiles will for sure be a fiasco. > > -Jukka Rahkonen- > _______________________________________________ > mapserver-users mailing list > mapserver-users@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/mapserver-users _______________________________________________ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users
