On Sat, Oct 5, 2013 at 3:31 AM, Rahkonen Jukka <[email protected]> wrote: > Hi, > > Have also definitely a try with JPEG compressed tiffs. You can save 90% of > the disk space with nominal effect on speed and quality, but that depends on > your hardware and imagery. It is still worth testing. The command to use is > gdal_translate -of GTiff -co tiled=yes -co compress=JPEG -co photometric=YCBCR > > For overviews use > gdaladdo -r average -ro --config COMPRESS_OVERVIEW JPEG --config > PHOTOMETRIC_OVERVIEW YCBCR > > With or without -ro is a matter of taste. By using internal overviews you > will save a bit more space because external overviews have some ballast but > if you want to archive images sometimes you can discard the external > overviews and save some disk space by that time. > > Tiffs are not as hopeless than plain JPEGs of PNGs and images do not need to > be read totally into memory. > Untiled tiffs are usually written in stripes so for reading a box from an > arbitrary place inside the image it is enough to read all the scan lines > which intersect that box. It is still more data than what is needed with > tiled images. > > There are also clever tiff readers which can read fast, let's say, every 10th > row and column from uncompressed tiff and create an subsampled, nearest > neighbour subsample in-the-fly. I have used one such in the 90's and Intel > 386 computers could handle pretty well uncompressed tiffs of size 10000x10000 > pizels without overviews. I think that GDAL can't do that kind of selecting > and this is more nice-to-know stuff from the stone age. What to remember is > that tiles and overviews are essential for GDAL and Mapserver.
Folks, Great advice from Jukka, and I'd just note that GDAL *will* efficiently pull out reduced resolution images on the fly without overviews if you have a file organized with a one scanline block even in the year 2013. For map serving you are still much better off for several reasons with the tiles+overviews approach, but I do love the properly that a one-block-scanline file can be quickly subsamled by viewer applications like OpenEV and QGIS. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, [email protected] light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Software Developer _______________________________________________ mapserver-users mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/mapserver-users
