[postgis-devel] [PostGIS] #1586: [raster] st_dumpaspolygons makes not valid polygons

[PostGIS]

#1586: [raster] st_dumpaspolygons makes not valid polygons
----------------------+-----------------------------------------------------
 Reporter:  jomarlla  |       Owner:  pracine      
     Type:  defect    |      Status:  new          
 Priority:  high      |   Milestone:  PostGIS 2.0.0
Component:  raster    |     Version:  trunk        
 Keywords:            |  
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Comment(by dustymugs):

 After doing some thinking about GDALPolygonize() and GDALFPolygonize()
 (both used by ST_DumpAsPolygons), it is possible/probably for invalid
 polygons to be generated.  From the GDAL API docs for GDALPolygonize:

 {{{
 This function creates vector polygons for all connected regions of pixels
 in the raster sharing a common pixel value
 }}}

 Two pixels with the same value with one common corner may cause a bow-
 tie...

 {{{
    +--+
    |  |
    |  |
 +--+--+
 |  |
 |  |
 +--+
 }}}

 I don't see any way to make GDAL generate valid polygons but we could add
 a validation routine to the appropriate C code in rt_api.c.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1586#comment:6>
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