Thanks Elijah, that thread does look promising. But it involves using gdal_polygonize.py, which is giving me trouble (we haven't tried GDAL/Python options before). Initial attempt at gdal_polygonize.py gives the error "ImportError: No module named gdal". After researching the archives, I found some advice from Howard Butler in October 2007 to go to the 'swig' directory and do 'nmake -f makefile.vc python'. Tried that, and it processed for awhile then quit with this error msg:
"error: Python was built with Visual Studio 2003; extensions must be built with a compiler than can generate compatible binaries. Visual Studio 2003 was not found on this system. If you have Cygwin installed, you can try compiling with MingW32, by passing "-c mingw32" to setup.py. NMAKE : fatal error U1077: 'C:\Python25\python.exe' : return code '0x1' Stop. " It's true, I don't have VS 2003, but I do have VS 2008 and VS 2010. Does anyone have setup advice on using gdal_polygonize.py on Windows 7 64-bit with GDAL 1.8.0 ? I have a feeling I'm missing something simple. We have GDAL 1.8.0 built from source, which works well, but we've never used the Python options. Most of the GDAL/Python discussions in the archives seem to be about Linux or Apple OS. Thanks for any guidance. PS I have Python 2.5 installed. --JJ -----Original Message----- From: Elijah Robison [mailto:[email protected]] Sent: Friday, April 22, 2011 3:05 PM To: Jay Jennings Cc: [email protected] Subject: Re: [gdal-dev] Polygonize from C# ? Hi Jay, you might want to review the following thread (Get extent from rasters). Based on a cursory read of his advice, I believe Trent offers a solution that might accommodate your task: http://lists.maptools.org/pipermail/fwtools/2010-October/001886.html /Elijah Jay Jennings wrote: > Correct, we just need the footprint of the "good" (non-NODATA) area, which > will often approximate a simple 4-point polygon with no holes. > > -----Original Message----- > From: Elijah Robison [mailto:[email protected]] > Sent: Friday, April 22, 2011 2:07 PM > To: Jay Jennings > Cc: [email protected] > Subject: Re: [gdal-dev] Polygonize from C# ? > > Jay, do you basically want a footprint shape of the useful data in the > Sat images (say, without the collar), or is the problem more complex, > where perhaps you have a mosaic of several images and, like swiss > cheese, there are no-data holes within the image? > > It sounds to me like you just want a footprint of the collarless area; > is this correct? > > /Elijah > > Jay Jennings wrote: > >> I see, thanks. But since I have satellite images, this part of the doc is >> alarming: "...For non-thematic raster data (such as satellite images) >> the result will essentially be one small polygon per pixel, and memory and >> output layer sizes will be substantial. The algorithm is primarily >> intended for relatively simple thematic imagery, masks, and classification >> results". >> >> I just want one polygon enclosing the non-zero pixels (or alternatively, >> enclosing the zero pixels, then I could do a geometric >> difference). Is there any way to trick the method into doing that, to maybe >> avoid the heavy resource needs ? >> >> >> -----Original Message----- >> From: Even Rouault [mailto:[email protected]] >> Sent: Friday, April 22, 2011 11:45 AM >> To: Jay Jennings >> Cc: [email protected] >> Subject: Re: [gdal-dev] Polygonize from C# ? >> >> Selon Jay Jennings <[email protected]>: >> >> Generally, refering to the C/C++ doc is a good way of finding the info : >> >> See http://gdal.org/gdal__alg_8h.html#3f522a9035d3512b5d414fb4752671b1 >> >> >> >>> Hi list, >>> Can anyone point to any guidance or (preferably) examples on using >>> GDAL.Polygonize() with C# bindings ? I see what the interface is, but there >>> are some unexplained parameters, e.g. "string[] options". >>> >>> My eventual goal is to open a raster and produce a WKT POLYGON string >>> enclosing the "good" (non-NoData) area of the raster. Thanks. >>> >>> ......................................................... >>> Jay Jennings >>> [email protected] >>> >>> >>> >>> >>> >>> >>> >> _______________________________________________ >> gdal-dev mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
