From: Muhammad R. <muh...@ya...> - 2005-05-10 02:58:19
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Hi All, Thank you for all your responses. I have created my own datastore for this situation. I wrap database datastore (PostGIS to be precised since this one that I tried), with my own datastore (I called it dbgrid datastore). When a query is requested, it will be passed through the underlying datastore. But the result will be encapsulated into different FeatureType. So instead of returning the geometry object, I make them as GridCoverage object. I saw in LiteRenderer source that raster will be drawn if the attribute name is "grid", so I made it as "grid". However I havent try to render the result. Dont know yet whether render will work as I expect it. I am not sure whether this is correct approach. --- Gabriel Roldán <gr...@ax...> wrote: > You're exactly right Paul, > and I would like to add an observation: > > Once we had raster support in Geotools and > Geoserver, it should be > pretty easy to setup a "tiled" dataset to the WMS. > Actualle the WMS spec > allows it by defining nested layers, and we just > would need to implement > nested layer configuration in Geoserver WMS. > I would be the same strategy I used with ArcIMS a > couple of times: > having a directory of images (jpeg + worldfile for > example) that > altogether conforms the tile. > this allows a kind of improvements like creating a > hand made pyramyd. > let me explain it further: you setup a bunch of > directories with the > same raster dataset, but each one resampled to be > half the resolution of > the "parent" one, and adjust the world files for > double the pixel size. > then configure each dataset inside the same parent > layer and its own > parent layer, to be visible at different scales. > > We did it to be able of serving large raster tiles > with success, since > it is practically undoable if the images are pretty > large (say, a tile > of 5000x5000 pixel images are about 90 MB in memory > each one), by > creating this rough pyramid you can improve > performance, though it > requires a bit of experimentarions to define the > number of resamples > needed and their visibility scales. > It would be better to use a smarter raster format > though, but if one is > forced this could be a useful tip. > So what said, if raster support is in place, just > adding nested layer > configuration to geoserver could solve the problem. > > best regards, > > Gabriel. > > Paul Ramsey wrote: > > > You guys are talking at cross purposes. Muhammad > was inquiring whether > > Geoserver (and by extension, Geotools) supports > tiling in the sense > > that Mapserver supports tiling. That is, whether > it supports building > > up data for mapping in a two stage process: (1) > access a "tile index" > > file or table that gives the spatial locations of > all the "real" data > > files and (2) open up only those real data files > that interact with > > the region of interest that will be drawn, and > draw them onto the > > map. Mapserver tiling is a way of managing a > classic grid-based GIS > > data set, and also provides a performance boost as > a handy bonus. > > > > In contrast, Martin is talking about internal file > format structures. > > Some files internally use a system much like the > mapserver system in > > order to ensure that data that is "related" is > stored in the same area > > of the file. This makes reading data out of the > file faster. As he > > noted, this tends to be restricted to TIFF > formats. > > > > The answer is "no", Muhammad, Geoserver / Geotools > do not currently > > have the idea of a "tiled" data source, although > it is certainly > > something one could add, particularly once the > raster formats are all > > in good nick. It really is a required feature for > publishing large > > raster data sets. > > > > P. > > > > On 8-May-05, at 2:12 PM, Martin Desruisseaux > wrote: > > > >> Chris Holmes a écrit : > >> > >>> I am not a raster expert, but I think we have > some sort of support for > >>> image formats. I am not sure if they support > tiling or not, however. > >> > >> > >> The supports for image tiling depends on two > conditions: > >> > >> 1) Using a format that supports it. Not all > formats support tiling. For > >> example GIF and PNG don't (as far as I know), > but TIFF and GeoTIFF > >> do. > >> > >> 2) On Geotools side, we should uses JAI's > "ImageRead" operation for > >> reading image (JAI has extensive support of > tiling). The JAI's > >> "ImageRead" operation is built on top of J2SE > javax.imageio but > >> add more functionalities (the basic > ImageReader.read(...) bundle > >> with J2SE doesn't support tiling). > >> > >>> And I'm pretty sure using a database to store > the stuff is not > >>> supported. > >> > >> > >> Right... > >> > >> Martin. > >> > >> > >> > ------------------------------------------------------- > >> This SF.Net email is sponsored by: NEC IT Guy > Games. > >> Get your fingers limbered up and give it your > best shot. 4 great > >> events, 4 > >> opportunities to win big! Highest score wins.NEC > IT Guy Games. Play to > >> win an NEC 61 plasma display. 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