[Geotools-gt2-users] Re: Features from Map

[Martin D. <mar...@no...>]

Hello Gayatri

Finally I had a look at the code you sent me last week (sorry for the 
delay). I saw many lines, but no closed shapes. It may be the reason why 
GeometryCollection give no output (it doesn't explains the infinite loop 
however).

If we wants to check if a point is inside a shape, GeometryCollection 
need closed shapes. We can said if a point is inside a circle, or a 
rectangle, or a polygon. But what is "inside" a line that goes from the 
bottom to the top of the screen? If you means a point located right on 
the line, GeometryCollection will not work for this case; it assumes 
that line width are 0 (which is consistent with java.awt.geom.Line2D. 
See the 'contains' method for Line2D in J2SE javadoc). Even if a line 
has some width on the screen, it is often a styling issue unrelated to 
the width of the feature in "real world".

So if I'm understanding right, you want to find which line is close to a 
point. If I'm understanding right, you can process as below:

   1) Iterate through each geometries.

   2) Get the PathIterator for current geometry. You can take the
      opportunity to ask for pixels coordinates if you want (through
      the AffineTransform argument).

   3) Iterate through each lines returned by the PathIterator.

   4) Use java.awt.geom.Line2D.ptLineDist(...) method in order to
      compute the distance between this line and yours point.

   5) Select the feature when the distance is below some
      threshold value.


Hope it help,

	Martin.