I finally got gdal_polygonize.py and tried it and generate a shapefile. I might not use it as a solution for what I described below but I would like to use it for other purpose. My understanding is this function merge contiguous cells with the same pixel value.
Can I use this function and specify a range of value? Example: merge contiguous cells having a value > 16 and < 19 thanks Steve Steve Toutant, M. Sc. Analyste en géomatique Secteur environnement Direction des risques biologiques, environnementaux et occupationnels Institut national de santé publique du Québec 945, avenue Wolfe Québec, Qc G1V 5B3 Tél.: (418) 650-5115 #5281 Fax.: (418) 654-3144 [email protected] http://www.inspq.qc.ca Frank Warmerdam <[email protected]>@lists.osgeo.org Envoyé par : [email protected] 17/07/2009 01:24 PM A [email protected] cc [email protected] Objet Re: [gdal-dev] RE clip intersected [email protected] wrote: > > I might try this..is it the good way to do what I need? > > 1- Use gdal_polygonize.py to create a boundary (excluding pixels with no > value) of each image and save the boundary as a .shp > 2- Somehow find the intersected region of the 2 polygons (boundaries) > created above and save the result to .shp > 3- Use gdal_rasterize on one of the original image to burn a nodata > value based on the polygon representing the intersection area > > I didn't try yet because I don't have gdal_polygonize.py > My installation is from MS4W and this script is not there. I just > install GDAL with OSGEO4w and it seems that this script doesn't exist. > > If the method above is valid, > - how can I create a boundary excluding pixels with nodata? > - And, of course, where can I get gdal_polygonize.py Steve, I would be tempted to do this process in raster space. Perhaps by warping both images into different bands of a mosaic file to get everything overlaying and then using some sort of raster modelling (perhaps via numpy in a python script) to zero out the one image where the other is set. I think the vector mask approach would be difficult, in part because the mask produced would be very fine grained. Depending on your need for precision you could just hand digitize a vector mask suitable to wipe out the overlapping area. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, [email protected] light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Programmer for Rent _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
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