specific raster queries

Erick Ferreira erick.ferreira at WINGSTELECOM.COM.BR
Thu Apr 6 11:43:32 EDT 2006


I would like to share our need in our current project. We have been thinking that maybe going for an effective implementation in MapScrip might be a gain for both MapServer and our product. 

We have been writing a service layer that is a dynamic library in C that exposes some raster utility functions. 
We would like to use only the exported mapscript symbols (from libmapscript.so).

One of the functions we have to expose in our library is supposed to fetch the raster values of a given layer band that lie on a client-defined line segment described in map coordinates.

Map Server 4.8.1 does not support a msRasterQueryByLine() method. Also, even the msRasterQueryByShape() function in fact queries the whole bounding box of the polygon, not the polygon itself. 
We found that the most obvious top level implementation of our feature would be accomplished by iterating over rasterQueryByPoint() on a Bresenham line-drawing algorithm basis.
Our tests proved the performance to be really inappropriate in this implementation, as expected.

Does anyone have any good idea for good performance? 
Also, would it make sense if we invested our time to develop such routines like queryByShape() and queryByLine() ? And being so, would that represent a real gain to MapServer project? 


More information about the mapserver-dev mailing list