Archive for December, 2008

Python FDO Spotted in the Wild

Posted by Jason Birch in FDO, Open Source on December 3, 2008

Sean’s right, it does look a lot like C++. Still, it enabled Rick to build a Linux-native SHP to SDF conversion tool when the alternative (actual C++) would have been painful. Good to see it being used!

-J

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SQLite Spatial Files in FME 2009 through the Magic of FDO

Posted by Jason Birch in FDO, FME, Formats, Open Source, Tutorial on December 2, 2008

Writing the FDO/GDAL style of SQLite spatial files (see previous post for details) just got a LOT easier for those of us using Safe Software’s FME Desktop, even the affordable Base edition.

Over the past month, developers at Safe Software and the author of the FDO SQLite provider have put some time into ensuring that the SQLite provider will work properly with FME 2009. Reading worked fine out of the box, but writing required a bit of effort. FME needed datastore creation and schema writing added to their generic FDO writer, and the FDO SQLite provider needed to account for the way that FME writes to multiple schemas.

Here’s how you can take advantage of this provider in FME (and in other FDO 3.3 consumers, such as MapGuide Open Source 2.0):

  • Download the unofficial binaries for the SQLite provider from my site
  • Open this zipfile and copy the SQLiteProvider.dll file into your FDO directory (default c:\Program Files\FME\plugins\fdo\)
  • Make a backup of the providers.xml file in that directory, and then edit the original, adding the contents of the sqlite_provider_entry.xml file in an appropriate location.

Once this installed, writing to SQLite from within FME is dead easy…

1. Add new FDO Destination Dataset:

2. Go to Settings and specify OSGeo.SQLite.3.3 as the provider name:

3: Specify the filename you want to write to:

4. Optionally, set a spatial reference system, and click on OK:

That’s it; now you can start adding tables to your SQLite file as you would any other destination dataset in FME!

As far as I know, Safe will not be distributing the SQLite provider directly with FME 2009 (it’s still in beta) primarily because the provider is not officially being released for FDO 3.3, and partially because the provider is still under heavy development. Fear not, though. I am building this provider against the 3.3 branch as often as necessary, and will post binaries as I do.

The relative ease with which this format was supported by FME can be attributed to Safe’s foresight in exposing FDO directly, rather than just using it behind-the-scenes in their SDF3 writer. They also allow FME to act as an FDO provider, which enables users of products that use FDO for their data layer (such as AutoCAD Map 3D) to access the full range of formats that FME supports.

-J

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Changing selection colour in MapGuide AJAX viewer

Posted by Jason Birch in MapGuide, OSGeo, Open Source, Tutorial on December 2, 2008

One of the annoyances that people have faced with MapGuide Open Source is that the selection colour was hard-coded in one of the C++ rendering functions. There were a few ways of getting around this without recompiling, but they were all a lot of work. RFC 38 included some code changes that made it possible to modify this value on the fly, but it doesn’t look like this capability was taken advantage of by the AJAX viewer that was distributed with MGOS 2.0.x.

If you’re using MapGuide Open Source 2.0 (2.0.2 recommended) and are not happy with the default blue selection colour, you can easily change it on a per-install basis by modifying the mapviewerajax template file. This is located at:

(INSTALLDIR)\WebServerExtensions\www\viewerfiles\ajaxmappane.templ

You will need to find the function called RequestMapImage, which includes a line that looks like this:


url = webAgent +
"?OPERATION=GETDYNAMICMAPOVERLAYIMAGE&FORMAT=PNG&VERSION=1.0.0&SESSION="
+ sessionId + "&MAPNAME=" + encodeComponent(mapName)
+ "&SEQ=" + Math.random();

You will need to modify this to change the VERSION to 2.0.0, and add the BEHAVIOR and SELECTIONCOLOR parameters:


url = webAgent +
"?OPERATION=GETDYNAMICMAPOVERLAYIMAGE&FORMAT=PNG&VERSION=2.0.0&SESSION="
+ sessionId + "&MAPNAME=" + encodeComponent(mapName)
+ "&SEQ=" + Math.random() + "&BEHAVIOR=7&SELECTIONCOLOR=FF5300FF";

Before:

After:

The BEHAVIOR parameter is a bitmask that controls what is rendered, and is described in RFC 38. The SELECTIONCOLOR parameter is a hex string in RGBA format, or its integer equivalent. Note for geeks: the A (opacity) portion of the string is ignored; the server code masks this out of the passed value, and then adds 200 (C8) as the line opacity and 160 (A0) as the fill opacity.

Note, the mapagent call allows you the flexibility to add more complicated behaviour to your viewer, such as changing the selection colour dynamically based on the map name, but I’ll leave that as an exercise for the reader (mostly because I’m lazy and use Fusion anyway and wouldn’t benefit from the work).

-J

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