That would be great if you can provide some suggestions, Michael.
My best idea for meeting Peter's requirement for preserving edge
information is to add an option to the polygonizer to keep lists of the
edge userdata as I outlined in my email. This could be incorporated in the
Polygonizer as it stands. And perhaps you have some further ideas for
making the Polygonizer more flexible.
On Tue, Nov 25, 2014 at 11:10 PM, Michael Michaud <
[email protected]> wrote:
> Hi,
> > Well, the original linestrings and the border/polygon hole line strings
> wouldn't necessarily be equal, correct? One option would be to first
> dissolve the line strings into segments, so that all resulting line strings
> were one segment long. Construct the hashmap from that set. Then after
> polygonization, you could walk the segments of the polygon linestrings and
> use the hashmap to determine the values of contributing line strings. If
> line string values are not unique, this method would require some tweaking.
> A few years ago, I had a similar problem where I wanted to keep
> relations between polygon and enclosing edges after polygonization. I
> had to hack Polygonizer. I hoped it would not be too much work, but
> because Polygonizer made many low-level methods private, I had to
> duplicate several classes.
> I think it would make things easier if Polygonizer itsef coud preserve
> information where it is possible, or if it could expose more methods in
> its api. I'll try to give more details about what I had to change, if I
> can retrieve it.
>
> Michaël Michaud
> >
> >
> >
> >> On Nov 25, 2014, at 4:48 PM, Michael Bedward <[email protected]>
> wrote:
> >>
> >> Hi Peter,
> >>
> >> Perhaps a HashMap of LineString -> Double will do the trick ?
> >>
> >> Michael
> >>
> >>> On 26 November 2014 at 05:29, Peter Kovac <
> [email protected]> wrote:
> >>> Hi JTS,
> >>>
> >>> I'm computing a polygonization of a large set of LineStrings (tens to
> >>> hundred thousands), each with one Double value as user data. What is
> the
> >>> most efficient way to determine for each resulting polygon the set of
> >>> Double values of LineStrings which are the borders of the polygon?
> >>>
> >>> Can I find by extending the Poylgonizer somehow (I think it's
> unlikely)?
> >>> Currently, I keep the input LineStrings in a SpatialIndex and query
> each
> >>> polygon coordinate for LineStrings containing it, but it's a very slow
> >>> process (tens of seconds).
> >>>
> >>> For example:
> >>> Let's give LineStrings in this MULTILINESTRING ((10 0, 0 0, 0 20, 10
> >>> 20), (10 0, 20 0, 20 20, 10 20), (10 0, 10 20)) values 1, 2, and 3
> >>> respectively.
> >>> Then the set of values of POLYGON ((10 20, 10 0, 0 0, 0 20, 10 20)) is
> >>> {1, 3} and of POLYGON ((10 20, 20 20, 20 0, 10 0, 10 20)) is {2, 3}.
> >>>
> >>> Thank you,
> >>>
> >>> --
> >>> Peter Kovac
> >>> MicroStep-MIS
> >>> Programmer
> >>> [email protected]
> >>> http://www.microstep-mis.com
> >>>
> >>>
> >>>
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