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List:       openjdk-2d-dev
Subject:    Re: [OpenJDK 2D-Dev] <AWT Dev> Question: Area changes order of points
From:       "Hruda, Steve" <steve.hruda () hexagongeospatial ! com>
Date:       2015-10-08 7:20:24
Message-ID: C7C75E3032555446BED1E26C40C3CE6601F30B97 () EU-MBX3 ! ingrnet ! com
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Hi Jim,
thank you for the insides!

We implemented a renderer which uses the OGC Symbology Encoding definition to style \
geometries and a polygon will not only stroke, it can also be filled. I removed the \
code which clips the geometry by using the area, to avoid your mentioned issues.

And yes the reason for that was to avoid the decoration-process outside of the clip.

In addition one of our developer (before my time ;-) ) solved printing problems. The \
colleagues  told me that big polygons like country frontiers produced line-fragments \
and the clipping of the geometries solved that issue. I wasn't able to reproduce that \
issue. Maybe this issue is already solved or it doesn't occur since we forced the \
print engine to use the raster pipeline.

Best Regards,
Steve




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-----Original Message-----
From: Jim Graham [mailto:james.graham@oracle.com]
Sent: Thursday, October 8, 2015 12:32 AM
To: Hruda, Steve <steve.hruda@hexagongeospatial.com>
Cc: 2d-dev <2d-dev@openjdk.java.net>
Subject: Re: [OpenJDK 2D-Dev] <AWT Dev> Question: Area changes order of points

Note that "Area" is specifically targeted to processing areas, not outlines.  While \
it does express its answer in the form of an outline, on the other hand the \
information it is processing, operating on, and representing internally is areas, not \
outlines.  It's output is intended only for filling, not for stroking.  You can \
stroke its output because the graphics system allows you to stroke any path, but the \
Area class wasn't concerned at all about stroking issues (such as path direction) \
during its internal operations.

If you are simply trying to simplify the polygon to throw out unnecessary segments to \
simplify rendering then the Area class is not designed or optimized to address your \
needs.  Additionally, it is doing way more work than your application needs and \
writing your own implementation may perform better.

Also, Area will perform optimizations that you don't want such as removing an \
interior segment that does not contribute to the boundary between interior and \
exterior.  Such segments are superfluous for filling, but might be visible when \
stroking.  The Area class won't care and will just delete them all the same because \
it only cares about areas internally.

Another issue to consider is that if you have arrows or other periodic decorations \
then removing segments will mean that those decorations will shift their locations.  \
The length of the omitted path must be considered while computing where the \
decorations are placed, but if you pre-edit the path to remove them then those \
lengths cannot be computed.

Out of curiosity, are you trying to clip these paths to avoid having to process \
decorations on parts of the path that are far outside of the clip?  We've recently \
discussed that performance issue internally in the Graphics-Rasterizer project and \
noted that it is an opportunity for future performance work...

                        ...jim

On 10/7/15 12:37 AM, Hruda, Steve wrote:
> Hi Jim,
> we are using the Area to clip/intersect geometries like a polygon. Such a polygon \
> has a digitizing direction and this direction has an effect on the point order. 
> If we visualize a clipped polygon in our map, than we have the problem that complex \
> line styles like a placed graphic along a line e.g. an arrow, shows in the wrong \
> direction. 
> Thanks for the explanation Jim, I will consider the point-order manipulation in our \
> application. 
> Regards,
> Steve
> 
> 
> 
> 
> Diese E-Mail wurde versandt im Auftrag des Unternehmens Intergraph Ges.m.b.H.
> Vertretungsberechtigte Geschäftsführer: Maximilian Weber Sitz der
> Gesellschaft: Margaretenstraße 70/I/1, 1050 Wien, Österreich, Tel. +43
> (1) 9610567-0 Eingetragen beim Handelsgericht Wien, Firmenbuch-Nr.: FN
> 116859 b Umsatzsteuer-Identifikationsnummer / VAT-ID: ATU15138401,
> Steuer-Nummer: 264/4807
> 
> This E-Mail has been sent on behalf of the company Intergraph Ges.m.b.H.
> Authorised Managing Directors: Maximilian Weber Registered office and
> Austrian headquarters: Margaretenstr. 70/I/1, 1050 Wien, Austria, Tel.
> +43 (1) 9610567-0 The company is recorded at the commercial court of
> Vienna under the company register number FN 116859 b
> VAT-ID: ATU15138401, Austrian Tax ID: 264/4807
> 
> Diese E-Mail (mit zugehörigen Dateien) enthält möglicherweise Informationen, die \
> vertraulich sind, dem Urheberrecht unterliegen oder ein Geschäftsgeheimnis \
> darstellen. Falls Sie diese Nachricht irrtümlicherweise erhalten haben, \
> benachrichtigen Sie uns bitte umgehend, indem Sie eine Antwort senden, und löschen \
> Sie bitte diese E-Mail und Ihre Antwort darauf. Sämtliche aufgeführten Ansichten \
> oder Meinungen sind ausschließlich diejenigen des Autors und entsprechen nicht \
> notwendigerweise denen des Unternehmens Intergraph. 
> This E-Mail (and any attachments) may be confidential and protected by legal \
> privilege. If you are not the intended recipient please notify us immediately by \
> replying to the sender and delete this E-Mail and your reply from your system. All \
> the views and opinions published here are solely based on the author's own opinion \
> and should not be considered necessarily as reflecting the opinion of Intergraph. 
> 
> -----Original Message-----
> From: Jim Graham [mailto:james.graham@oracle.com]
> Sent: Tuesday, October 6, 2015 8:38 PM
> To: Hruda, Steve <steve.hruda@hexagongeospatial.com>
> Cc: Sergey Bylokhov <Sergey.Bylokhov@oracle.com>; 2d-dev
> <2d-dev@openjdk.java.net>
> Subject: Re: [OpenJDK 2D-Dev] <AWT Dev> Question: Area changes order
> of points
> 
> Hi Steve,
> 
> Area simplifies the shape into a normalized version that defines the same interior \
> area.  It does not care what the original ordering of the points was as it \
> internalizes the shape, all it cares about is which areas are geometrically inside \
> vs. outside and it creates a path according to its own internal policies that \
> defines the same inside/outside boundaries. 
> There is no "trick" to customizing this behavior and I'm not entirely sure why the \
> point ordering would matter when you are performing CAG (Constructive Area \
> Geometry) operations - only interiors and exteriors should matter. 
> ...jim
> 
> On 10/5/15 8:19 AM, Sergey Bylokhov wrote:
> > Hello,
> > I think this question is related to java2d, correct alias cc.
> > 
> > On 24.09.15 12:53, Hruda, Steve wrote:
> > > I use the java.awt.geom.Area class to clip a shape. Today I noticed
> > > that new Area(Shape) changes the orientation of the shape, so that I
> > > get the points of the Area counter-clockwise in every case.
> > > 
> > > The following test shows you my problem.
> > > 
> > > https://drive.google.com/file/d/0B7P_rknS1TWxVGJ6a3hBaElBTk0/view?us
> > > p
> > > =sharing
> > > 
> > > 
> > > Is this a bug or do I something wrong?
> > > 
> > > Is there a trick to get the points in the correct order?
> > 
> > 
> 


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