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<div class="moz-cite-prefix">Hi all<br>
<br>
I had a detailed look with the debugger at what happens in the
different versions. It turned out fTools does indeed handle
geometry collections, but assumed a geometry collection has wkb
type 'unknown' (which was true <= 2.8, but now geometry
collections are not unknown anymore). Commit
<a class="moz-txt-link-freetext" href="https://github.com/qgis/QGIS/commit/594fafe73b80d91d94b962c2e51aea0b0168a08a">https://github.com/qgis/QGIS/commit/594fafe73b80d91d94b962c2e51aea0b0168a08a</a>
should solve the issue and bring back the old behaviour.<br>
<br>
Regards,<br>
Marco<br>
<br>
<br>
<br>
On 24.11.2015 11:29, Marco Hugentobler wrote:<br>
</div>
<blockquote cite="mid:56543BF1.3070402@sourcepole.ch" type="cite">
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<div class="moz-cite-prefix">On 24.11.2015 11:13, Matthias Kuhn
wrote:<br>
</div>
<blockquote cite="mid:56543846.1060405@opengis.ch" type="cite">
<meta content="text/html; charset=utf-8"
http-equiv="Content-Type">
Hi Marco<br>
<br>
<div class="moz-cite-prefix">On 11/24/2015 11:01 AM, Marco
Hugentobler wrote:<br>
</div>
<blockquote cite="mid:5654358D.2060903@sourcepole.ch"
type="cite">
<meta content="text/html; charset=utf-8"
http-equiv="Content-Type">
<div class="moz-cite-prefix">Hi Alessandro, Matthias<br>
<br>
>Is there no requirement for multi types?<br>
<br>
Afaik, the problem for f-tools are not the multi types, but
only the geometry collections (containing geometries with
different shape type). In my experience, if geos returns a
geometry collection, it usually contains one 'expected'
geometry and the others are slivers (@strk, please correct
me if wrong).<br>
</div>
</blockquote>
<br>
I was mostly thinking about collections that contain a multitype
with several parts which are not considered slivers. This seems
to be a very valid scenario.<br>
</blockquote>
<br>
It is, but it was also not handled by f-tools <= 2.8.<br>
<br>
<blockquote cite="mid:56543846.1060405@opengis.ch" type="cite"> <br>
<blockquote cite="mid:5654358D.2060903@sourcepole.ch"
type="cite">
<div class="moz-cite-prefix"> <br>
>Based on what indicator should be chosen what to
extract? Try polygons first, if there are none try lines, if
there are none take points? <br>
<br>
One possibility would be to pass the expected shapetype
(Point / Line / Polygon) to the function and take the best
candidate (e.g. longest line, largest polygon area).<br>
</div>
</blockquote>
<br>
Before the geometry changes, the algorithms were able to provide
the results without this additional information. How was that
done?<br>
</blockquote>
<br>
Not sure. Maybe the logic in the geos -> QgsGeometry conversion
handled the collections differently.<br>
<br>
<br>
Regards,<br>
Marco<br>
<br>
<br>
<br>
<blockquote cite="mid:56543846.1060405@opengis.ch" type="cite"> <br>
<blockquote cite="mid:5654358D.2060903@sourcepole.ch"
type="cite">
<div class="moz-cite-prefix"> <br>
>How much effort (in time) do you think is required to
implement this fix?<br>
<br>
Difficult to estimate. It seems straightforward to implement
the extraction function. Then it needs to be called by the
f-tools internally and be tested with a few examples. If
unit tests are required (as mentioned by Alessandro), this
seems to be the most time consuming task to me. <br>
</div>
</blockquote>
Unit Tests for processing are on my todo list anyway (I think as
a psc member you should have voted for that ;) )<br>
<br>
Matthias<br>
<blockquote cite="mid:5654358D.2060903@sourcepole.ch"
type="cite">
<div class="moz-cite-prefix"> <br>
Regards,<br>
Marco<br>
<br>
On 24.11.2015 10:42, Matthias Kuhn wrote:<br>
</div>
<blockquote cite="mid:565430F2.70305@opengis.ch" type="cite">
<meta content="text/html; charset=utf-8"
http-equiv="Content-Type">
Hi Marco<br>
<br>
Good to have your feedback, you probably know the problem
best.<br>
<br>
<div class="moz-cite-prefix">On 11/24/2015 09:28 AM, Marco
Hugentobler wrote:<br>
</div>
<blockquote cite="mid:56541FA7.8070707@sourcepole.ch"
type="cite">
<meta content="text/html; charset=utf-8"
http-equiv="Content-Type">
<div class="moz-cite-prefix">Hi<br>
<br>
>ad issue 1: update fTools to warn users when some
features cause problems<br>
>ad issue 2: quick fix fTools to convert geometry
collections to single geometry types<br>
<br>
A function that takes a geometry type and extracts the
longest line / the largest polygon / the first point
from the geometry collection should be straightforward
to do.<br>
</div>
</blockquote>
<br>
Is there no requirement for multi types?<br>
Based on what indicator should be chosen what to extract?
Try polygons first, if there are none try lines, if there
are none take points?<br>
<br>
<blockquote cite="mid:56541FA7.8070707@sourcepole.ch"
type="cite">
<div class="moz-cite-prefix"> <br>
>These fixes/updates would be made available as
fTools updates via the plugin installer asap<br>
<br>
If the fix does not take too long, we probably don't
need a warning at all.<br>
</div>
</blockquote>
<br>
How much effort (in time) do you think is required to
implement this fix?<br>
<br>
Regards,<br>
Matthias<br>
<br>
<blockquote cite="mid:56541FA7.8070707@sourcepole.ch"
type="cite">
<div class="moz-cite-prefix"> <br>
Regards,<br>
Marco<br>
<br>
On 23.11.2015 21:35, Anita Graser wrote:<br>
</div>
<blockquote
cite="mid:CAFFV8FgYvYzu+eDGjiA90UtfkryMUHjs_dd9_soS4osRp2m5Ew@mail.gmail.com"
type="cite">
<meta http-equiv="Context-Type" content="text/html; ">
<div dir="ltr">
<div class="gmail_default">Hi,</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">If you are following the
psc list, you've probably seen the thread discussing
current shortcomings of ftools (<a
moz-do-not-send="true"
class="moz-txt-link-freetext"
href="http://lists.osgeo.org/pipermail/qgis-psc/2015-November/003623.html"><a class="moz-txt-link-freetext" href="http://lists.osgeo.org/pipermail/qgis-psc/2015-November/003623.html">http://lists.osgeo.org/pipermail/qgis-psc/2015-November/003623.html</a></a>)</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">In short, the key issues
are:</div>
<div class="gmail_default">1. When ftools encounter
issues with certain features, warning messages get
written to the log but this is largely hidden from
users since they would actively have to actively
monitor the log. The problematic features are then
missing from the results but this is not always
obvious. </div>
<div class="gmail_default">2. The above issue is more
common now (since 2.10) since underlying libraries
more often (and correctly so) produce geometry
collections as outputs. These geometry collections
are not handled well by the current ftools code
which is much older.</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">To address these issues,
the following suggestions have been made so far: <br>
ad issue 1: update fTools to warn users when some
features cause problems<br>
ad issue 2: quick fix fTools to convert geometry
collections to single geometry types</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">For the warnings, there's
already a first PR draft <a moz-do-not-send="true"
href="https://github.com/qgis/QGIS/pull/2432">https://github.com/qgis/QGIS/pull/2432</a>
which needs to be fleshed out. </div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">These fixes/updates would
be made available as fTools updates via the plugin
installer asap. </div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">If you have ideas how to
handle this efficiently or have already implemented
code that addresses similar issues, let us know. </div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">It would be good to have a
quick discussion in order to be able to provide
improvements fast.<br>
</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">Best wishes,</div>
<div class="gmail_default">Anita</div>
</div>
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Dr. Marco Hugentobler
Sourcepole - Linux & Open Source Solutions
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OPENGIS.ch - <a moz-do-not-send="true" class="moz-txt-link-freetext" href="https://www.opengis.ch">https://www.opengis.ch</a>
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Dr. Marco Hugentobler
Sourcepole - Linux & Open Source Solutions
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OPENGIS.ch - <a moz-do-not-send="true" class="moz-txt-link-freetext" href="https://www.opengis.ch">https://www.opengis.ch</a>
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