[Nrdbpro-developer] NRDB Web optimisation

[Natural R. D. <nr...@my...>]

For those who've tried the NRDB Web demo, you may have noticed it 
taking quite a long time to display the image (compared to a few days 
ago).

http://www.mypalawan.info/nrdb/temp/index.php

Since PHP is interpreted its pretty slow at iterative loops (for, 
while, multiple calls to imageline).  Whereas built in functions for 
handling blocks of data (like 'pack' and 'imagepolygon' are quite 
fast).  I therefore intend to optimise how the polygons are stored in 
the database such that:

- the centroid and extent may be pre-calculated and stored
- the vertices are stored as arrays of integers (rather than run length 
encoded), so that they can be extracted with single function calls
- the vertices are generalised to reduce the size of arrays (remove 
duplicate vertices that would relate to the same pixel when displayed)

At present I'm just focussing on the database functions - the current 
mapping/interface is just for testing purposes.

Richard