[geos-devel] Geometry/Rectangle Intersection: line touching rectangle

[Sandro Santilli]

On Wed, Sep 10, 2014 at 06:59:53PM -0700, Martin Davis wrote:
> Sandro, are the two cases below currently in JTS?  If not I should add
> them...

I hadn't checked, but I'm using GEOS results as reference, so it gives
the results I'm reporting already.

Actually one result I'm looking at is perplexing.
One operand is the usual rectangle, the other is a polygon which
is cut by the right-edge of the rectangle and has a rectangular
hole whose right edge is covered by the rectangle edge:

 POLYGON(
  (5 2,5 8,15 8,15 2,5 2),
  (8 4, 8 6, 10 6, 10 4, 8 4)
 )

10 +-----------+
   |           |
 8 |    +------+----+
   |    |      :    |   h: hole
 6 |    |  +---+    |   s: shell
   |    |  | h |    |   
 4 |    |  +---+    |
   |    |      :    |
   |    |   s  :  s |
 2 |    +------+----+
   |           |
 0 +-----------+
   0    5  8  10   15

GEOS intersection result is:

 GEOMETRYCOLLECTION (
   POLYGON ((8 4, 8 6, 10 6, 10 4, 8 4)),
   LINESTRING (10 2, 5 2, 5 8, 10 8)
 )

Visually:

10 . . . . . . .
   .           .
 8 .    +------+     
   .    |      .        
 6 .    |  +---+       
   .    |  |   |        
 4 .    |  +---+     
   .    |      .     
   .    |      .     
 2 .    +------+     
   .           .
 0 . . . . . . .
   0    5  8  10   15

Does JTS give the correct answer for that ?

--strk;