I've got an initial refactoring of cscs checked in for comment as
cscs/lib/proj4js.js. It is mostly jjust re-arranging things to be a
little more object-oriented using Prototype.js - all the actual
calculations are the same.
Highlights:
- uses it's own namespace called Proj4js - I can live with cscs as the
library name but I will make an impassioned plea to change the name of
this library to Proj4js because I think it is much more descriptive of
what it does and where it came from
- look up projection definitions from memory, loaded in from disk, or
failing that then it uses the new spatialreference.org lookup service
with an Ajax request. This part is really cool because it means you
don't necessarily have to know the proj parameters beforehand.
- will dynamically load projection class code from disk, e.g. lcc.js or
these may also be loaded in your application HTML HEAD element
- offers the following API (this is a rough sketch, I would like to
document this for NaturalDocs)
Proj4js //global Namespace object, with some init properties
Proj4js.defs. //hash of all the proj definitions loaded, as Proj4
command line options
//this could also use JSON, WKT, etc. formats
eventually
Proj4js.defs.EPSG4326 //for example
Proj4js.proj //abstract proj object, constructor takes single srsCode
argument
//which offers the following methods
Proj4js.proj.transform(point, dest) //transform point from this proj
into the dest proj
Proj4js.proj.forward(point) //transform point from lon,lat
to proj x,y
Proj4js.proj.inverse(point) //transform point from proj
x,y to lon,lat
Proj4js.proj.lcc //class containing the actual code for LCC projection,
one for each projection type, etc.
Proj4js.datums //not yet completed, but will handle datum transformations
To use a Proj4js object:
var myProj = new Proj4js.proj(srsCode) ;
var newPoint = myProj.transform(point, yourProj) ;
The implementation is a little weird in that your will always request a
Proj4js.proj object, but what you get back is actually Proj4js.proj.lcc
if you ask for a LCC projection for example. I think this is OK because
they all offer transform(), forward() and inverse() methods.
I haven't checked in a working example in SVN yet, but I do have it
running on my machine and it works well. I will wait for comments on
thee naming issue and if this API seems to be acceptable to everyone.
Mike
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