Free Software

Hello, Burt!

Following our first album togheter, and after moving to Siena for taking formal music studies, me and Elisabetta have started a new project with a local guitarist and a new setup: she plays bass in this combo. The bass was sold to her by Fabio, a friend of mine who wasn’t finding the time to play it. That friend was the inspiration for me to play the songs written by Burt Bacharach, who I did not know much about, before Fabio mentioned him to me.

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Slivers of life

The first album of our jazz trio is finally completed. It took a few months to find the time to sit together in the wonderful tiny studio of Danilo, the pianist and producer. It didn’t help that me and Elisabetta, the singer, moved 3 hours away from the studio to attend a jazz accademy, following our hearts. I’m playing the trumpet, a small and lovely instrument I’ve had the pleasure to start playing around spring 2017, blowing into it daily ever since.

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Trac from Mutt

Dedicated to those who do not want to surrender to proprietary services for code and tickets management: integrating Cartman with Mutt. The scenario is Trac instances that send email notifications on ticket activity, as is the case with the OSGeo ones (there’s been some recent discussion about the role of its infrastructure). The Cartman command to comment on a ticket (say #33) of a project (say postgis) would be: cm -s postgis 33 As you usually comment on some input received by mail (either a new ticket or another comment), building that command line requires eye-parsing for project name and ticket number, and then typing it on the shell.

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On the fly simplification of topologically defined geometries

Keeping GIS data in full-resolution and simplifying it on demand is a known challenge: simplification has to be fast and its output has to be topologically consistent. We saw how to get a topologically consistent simplified version of a full layer, but that method isn’t fast enough for on-demand usage. Also, we saw how to perform a fast simplification by sacrificing the degree or generalization so that the introduced inconsistency would not be visible on a rendering surface.

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GEOS 3.3.4 released

New bug fix and improvement release for the 3.3 series of GEOS is out. Changes since 3.3.3: Do not abort on NaN overlay input (#530) Reduce CommonBitsRemover harmful effects during overlay op (#527) Better cross-compiler support (#534) Enable overlay ops short-circuits (#542) Envelope-based short-circuit for symDifference (#543) Fix support for PHP 5.4 (#513) Fix TopologyPreservingSimplifier invalid output on closed line (#508) Reduce calls to ptNotInList, greatly speeding up Polygonizer (#545)

Simplifying a map layer using PostGIS topology

The data French administrative subdivisions, called “départements”, will be used. Data can be downloaded here. It is composed by 96 multipolygons for a total of 47036 vertices. Principle of simplification We convert a layer’s Geometries to TopoGeometries We simplify all edges of the built topology We convert the (now-simplified) TopoGeometries back to Geometries Steps The following steps assume you loaded the shapefile into a table named “france_dept”. The SimplifyEdgeGeom function You may have noticed that the “SimplifyEdgeGeom” is not a core function.

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PostGIS 2.0.0 released

The long-awaited full featured PostGIS 2.0.0 is finally out. Coupled with GEOS 3.3.3 (released a few days before) and GDAL-1.9.0, it brings you the best spatial database system in town, complete with raster analysis and topology modeling support. Complete announcement, with list of changes, here. It’s been an great pleasure to work with the rest of the team on getting this release ready for shipping, drawing a line after over two years of hard work on new features.

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Gnash 0.8.10 released

After one year of gestation, Gnash 0.8.10 is finally out. It fixes many compatibility issues (fixing from Google Dict to Camtasia and Captivate outputs, to a while category of interactive games), enhances user experience (popups on limits hit, gnome thumbnailer, QT4 mousewheel support), implements more of the SWF8 specs (BitmapData perlin noise), introduces new accelerated renderer (OpenVG) and better framebuffer GUI (touchscreen aware). This is the first Gnash release after Adobe announcement of giving up Flash for HTML5 in the mobile market.

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A walk on the wild side

I’ve been spending the last few days profiling and optimizing the new simple-to-topological converter you will find in PostGIS 2.0.0 thanks to a community effort. The most expensive operation was found to be the ST_AddEdgeModFace function, which adds an edge and checks if such edge creates a new face. Face-splitting detection was implemented using a brute force approach consisting in invoking the GEOS polygonizer and then checking if any polygon created contained the newly added edge in its boundary.

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GEOS 3.3.2 released

The second bugfix release in the 3.3 branch of GEOS was released today. This is the version required by the topology support shipped with the upcoming PostGIS 2.0 release. Everyone is recommended to upgrade. Changes can be read here, package can be downloaded here.