[gdal-dev] Closing disconnected contours
Hi, I have shape file from sample map, consisting of topological contours. However many contours have small gaps and I'm looking for a pointer how to connect those lines, automatically. Does ogr have a method or maybe more generally does anyone know of a tool, that would correctly close disconnected contours, which aren't labeled? Gaps are small - artifacts from graticules present in original image used as source for creating this vector. Thanks ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Closing disconnected contours
zeta, The gaps are likely caused by pixels with no data. A simple method is to run gdal_fillnodata.py on the original raster and then create the contours. http://www.gdal.org/gdal_fillnodata.html On Mon, Feb 25, 2013 at 1:01 PM, zeta ot...@hush.ai wrote: Hi, I have shape file from sample map, consisting of topological contours. However many contours have small gaps and I'm looking for a pointer how to connect those lines, automatically. Does ogr have a method or maybe more generally does anyone know of a tool, that would correctly close disconnected contours, which aren't labeled? Gaps are small - artifacts from graticules present in original image used as source for creating this vector. Thanks ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Best regards, Chaitanya kumar CH. +91-9494447584 17.2416N 80.1426E ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Closing disconnected contours
zeta, Are the lines in topo.tif contour lines? How did you generate them? On Tue, Feb 26, 2013 at 12:20 AM, zeta ot...@hush.ai wrote: Chaitanya kumar CH wrote: zeta, The gaps are likely caused by pixels with no data. A simple method is to run gdal_fillnodata.py on the original raster and then create the contours. http://www.gdal.org/gdal_fillnodata.html Thanks Chaitanya, that's excellent news, as I previously searched for algorithms about curve reconstruction, and none seemed easy for implementation. I was driven by approach using Delaunay Triangulation, referenced to Amenta The crust and the beta -skeleton: Combinatorial curve reconstruction and plastically explained i.e. here: http://valis.cs.uiuc.edu/~sariel/research/CG/applets/Crust/Crust.html but I thought to look for shortcut if possible, without reinventing implementation. I tried the script, and I get some gaps filled, but most aren't. I used -md parameter of 20px, but changed that value from 10 to 300 without significant improvement. Then I used mask file, which I assume works as in OpenCV Inpaint function, by using mask as a helper for gap detection, but without success. I'm attaching example image, and mask image, which I used to test the script, in a hope that someone can tell me if better results are possible. Thanks -- Best regards, Chaitanya kumar CH. +91-9494447584 17.2416N 80.1426E ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Closing disconnected contours
Chaitanya kumar CH wrote: Are the lines in topo.tif contour lines? How did you generate them? Hi Chaitanya, I segmented scanned image, and then did thinning on separation that interested me - that is topo contours. Here is link to a part of scanned image that I used as example: http://i.imgur.com/Wyv147m.png I thought also that maybe gdal_fillnodata.py doesn't like thinning (1px contours) and I did dilation on same image to get topo contours with 3px width, but result was worse. Did I expected too much, or maybe my image wasn't prepared corectly for gdal algorithm used in gdal_fillnodata.py? ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Closing disconnected contours
zeta, gdal_fillnodata is intended for raster images, like a DEM. Your image is a rendered map. The image you provided is not suitable for unsupervised processing, especially with GDAL. On Tue, Feb 26, 2013 at 12:53 PM, zeta ot...@hush.ai wrote: Chaitanya kumar CH wrote: Are the lines in topo.tif contour lines? How did you generate them? Hi Chaitanya, I segmented scanned image, and then did thinning on separation that interested me - that is topo contours. Here is link to a part of scanned image that I used as example: http://i.imgur.com/Wyv147m.png I thought also that maybe gdal_fillnodata.py doesn't like thinning (1px contours) and I did dilation on same image to get topo contours with 3px width, but result was worse. Did I expected too much, or maybe my image wasn't prepared corectly for gdal algorithm used in gdal_fillnodata.py? -- Best regards, Chaitanya kumar CH. +91-9494447584 17.2416N 80.1426E ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Closing disconnected contours
Chaitanya kumar CH wrote: gdal_fillnodata is intended for raster images, like a DEM. Your image is a rendered map. The image you provided is not suitable for unsupervised processing, especially with GDAL. OK than, Chaitanya, thanks for letting me know. Cheers ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
