Proof of Concept Gradient Coloring and Dev question

[Bart van den Eijnden]

Hi Bill,

Frank Warmerdam had this functionality (color-ramp) on his wishlist so you may want to check with him for ideas.

General procedure would be opening up a bugzilla entry and add the patch as an attachment, and then send out a short e-mail to the mapserver-dev list with a link to the bug report. The bugzilla entry can then also be used to discuss the final implementation.

There is a Mapserver CVS, although only the (core) developers have CVS write access. So probably one of the developers with CVS write access should apply your patch/feature (after they agree with the implementation ofcourse).

Best regards,
Bart

Met vriendelijke groet,

Bart van den Eijnden
GIS specialist
Syncera IT-Solutions

>>> Bill Binko <bill at BINKO.NET> 04/04/05 11:27pm >>>
Hi everyone,

I have just implemented a quick hack to add gradient coloring to mapserver
4.4.1.  This was just an itch I was scratching, but I'd be happy to feed
it back into the code.  My main question here is how do I do that: is
there a CVS repository?  Do I mail in patches?  To whom?

Regarding the gradient coloring, it works like this:  you choose a numeric
field in your data (I've tested with PostGIS, but anything you can use for
classitem or labelitem should work), and create a style like this:

STYLE
  COLOR 60 60 60
  MINCOLOR 0 0 0
  MAXCOLOR 255 255 0
  MINVALUE 0.0
  MAXVALUE 300000.0
  GRADIENTITEM "sale_price"
END

That takes the sale_price field from the shapes values, maps its value to
a percentage between MINVALUE and MAXVALUE and then picks the color that's
appropriate from the color range.

For a quick snapshot of how this looks, I've mapped relative size of
parcels (as a percentage) to these colors:

                MINCOLOR 127 29 200 #Purple
                MAXCOLOR 255 255 0  #Yellow

You can see the results here: http://www.binko.net/gradient.png 

As I said, this is still in the proof of concept stage, and I haven't
tested against any rendering except GD (although in theory it should
work).

Any help on future direction and how to contribute back would be
appreciated.

Bill