Kami ROUSSEAU wrote: > Hello, > > I have a tiff file that contains a full size 16Kx16K image, compressed using > JPEG. The file also contains ten reduced size overviews. When this image is > opened in gvSIG, the overviews are not used; instead, the full size image is > red in memory. This reading operation takes a long time to complete. > > I know that Java Advanced Imaging (JAI) can handle image pyramids and that > Geotools uses this capability. I also know that gdal can use image pyramids. > Quantum GIS uses gdal to display an overview of the image. > > Is there an existing automatic or semi-automatic way to read an > appropriately sized overview instead, using gvSIG / jgdal?
Kami, I'm not sure if this is the right list for this question. I'm not sure just how gvSIG works but if it ends up calling the GDALRasterIO() or GDALDatasetRasterIO() function all it needs to do to take advantage of overviews is to request a window with more pixels and lines than the buffer it is reading into. For instance to request the whole 16Kx16K image but to define a buffer to load into that is 1K x 1K should automatically use the x16 overview level (or nearest appropriate one if that does not exist). > If so, what is it? If not, what development would be necessary? What are the > relevent libraries / classes? Is there any reading material that could help? I assume that gvSIG does not use GeoTools' imagery API when going through GDAL (correct me if I'm wrong!) so I'd imagine any work would be within the gvSIG raster rendering logic. When I started composing this email I was also thinking to ask for a tiffinfo report on the file to be sure the overviews are setup in a gdal compatible way, but you can also just check with gdalinfo if overviews are reported. 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 Programmer for Rent ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Geotools-gt2-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-gt2-users
