AW: AW: [OpenMap Users] Areas with holes

Hi George,

i'm importing esri-shape files. For each "esri"-polygon you get am array of polygons.
One is the shape the others are the holes. Unfortunately the is no order in the array.
So you can't say the first polygon is the shape the others are the holes.

I need a method like

        polygons = makeShapeFirst(polygons);

Which puts the shape at index 0 and the holes at index 1..n

Yours Ruediger

-----Ursprüngliche Nachricht-----
Von: George Uecker [mailto:george.uecker@dot21rts.com]
Gesendet: Mittwoch, 30. April 2003 17:20
An: Gubler, Rüdiger
Cc: Openmap-Users (E-Mail)
Betreff: Re: AW: [OpenMap Users] Areas with holes

Hi Ruediger,

Gubler, Rüdiger wrote:

>Hi George,
>
>thank you this is what i need. My holes are also different areas, so first i must
>calculate the shape and the holes. Do you know a tricky solution?
>
I'm not sure I understand your question - can you elaborate a little
about your data and how you expect to see it displayed in your layer?

In my layer, I'm displaying contour isolines that have been calculated
from a radar clutter cell matrix using a customized version of CONREC.
  <http://astronomy.swin.edu.au/%7Epbourke/projection/conrec/> I simply
create OMPolys from the generated points and go from there according to
the steps outlined in my previous post.

Note that holes are only a problem if you are color- or pattern-filling
your areas. If you only draw the outline of the areas, there is no issue.

Regards,

George

>
>
>Yours Ruediger
>
>
>
>-----Ursprüngliche Nachricht-----
>Von: George Uecker [mailto:george.uecker@dot21rts.com]
>Gesendet: Montag, 28. April 2003 17:26
>An: Gubler, Rüdiger
>Cc: Openmap-Users (E-Mail)
>Betreff: Re: [OpenMap Users] Areas with holes
>
>
>Hi Rudiger,
>
>Here is what I did in my custom layer to display holes within OMPolys:
>
>Note: In my case, a "hole" is defined just like other areas, except that
>it happens to lie completely within the bounds of another area.
>
>Step 1: Create an OMPoly for each area. As each poly is created, you
>may have to call setDoShapes(true) on the OMPoly , depending on the
>version of OpenMap that you're using.
>
>Step 2: Generate the OMPolys for the current projection.
>
>Step 3: Call getShape() on each OMPoly. This method returns a
> java.awt.geom.GeneralPath object.
>
>Step 4: Create a new java.awt.geom.Area object from each GeneralPath object.
>
>Step 5: Use the Area.exclusiveOr() method to create a single compound
>Area that is the union of all Areas minus any intersection. Holes are
>the intersection of two Areas. Be aware that the exclusiveOr() is an
>expensive operation - you may want to do some pre-processing of each
>Area using bounding boxes to determine when it's actually necessary.
>
>Step 6: Use the Graphics2D.fill(Shape) method to render the resulting
>compound Area. Arbitrarily complex background layers will show through
>the holes as expected.
>
>Note that there are other ways to deal with holes - this way happens to
>be relatively easy to code, but it can be slow depending on the number
>of areas you have.
>
>Hope this helps,
>
>George
>
>Gubler, Rüdiger wrote:
>
>>Hi all,
>>
>>in which way can I handle areas with holes?
>>Does OpenMap can handle it in feature versions ?
>>
>>
>>Yours
>>Ruediger Gubler
>>--
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>>
>>.
>>
>
>

-- 
George Uecker				george.uecker@dot21rts.com
Software Engineer                       (410) 480-7236
Dot21 Real-Time Systems Inc.            (410) 313-7515 fax
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