From: <chr...@nv...> - 2011-02-03 11:46:16
|
Yep, exactly this bug happens here. An Oracle Georaster Object is basically a BLOB with extra features - georeferencing - inner tiling - pyramids You can compare such an object with a geotff file. This proposal has the following architecture. - You have a big base image. - Generate the tiles for the base image - Import the tiles into an Oracle table, each tile is GeoRaster Object - Generate the pyramids for each tile separately using GeoRaster code. But this code is not aware of neighbor tiles, the bug happens. - On request, fetch the tiles for the proper pyramid level and mosaic the result image in Java Oracle supports Nearest Neigbour, Bilinear (4 Pixels), Cubic (16 Pixels ), Average4 (4 Pixels) and Average16 (16 Pixels). That is the reason why I have headaches with this proposal. What do you think ? Quoting Andrea Aime <and...@ge...>: > On Wed, Feb 2, 2011 at 5:33 PM, <chr...@nv...> wrote: >> ??? I do not understand at all. >> Within the new extended border, I need the pixels from the neighbor tiles. >> >> Normally, if I have a big image, >> I create the pyramids and finally create the tiles for all levels. >> >> If I create the the tiles first and the pyramids for each tile individually, >> it is possible that the tiles are different. > > That may be a bug in the tile creation process? > > If the tile creation itself is using bilinear/bicubic interpolation > the proper way to > do compute a tile at level N is not to take just 4 tiles at level N - 1, but > also all the neighbouring tiles in order to include the necessary border > for the interpolation to work, crop so that only the required extra border > is taken into account, rescale with interpolation, crop again to remove the > eventual extra pixels that get in the result as an effect of having > considered > the extra border. > If a tile happens to sit at the overall mosaic limits add a copy > border extender > to care for that case. > > The javax.media.jai.Interpolation class do provide information about how big > the border should be in each direction (see the get*Padding methods) > > Cheers > Andrea > > > -- > Ing. Andrea Aime > Technical Lead > > GeoSolutions S.A.S. > Via Poggio alle Viti 1187 > 55054 Massarosa (LU) > Italy > > phone: +39 0584962313 > fax: +39 0584962313 > > http://www.geo-solutions.it > http://geo-solutions.blogspot.com/ > http://www.linkedin.com/in/andreaaime > http://twitter.com/geowolf > > ----------------------------------------------------- > ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program. |