(Prelim) Gradient Support for Mapserver 4.4.1

[bill@…]

As I posted on the mapserver-users list, I have put together a hack to get
gradient colors from a single style.  Here is the post:

...

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).

I have gotten some feedback from the -users group, but I'd appreciate any from
the core developers.  I will post a patch against 4.4.1 as well.

Bill