Changes between Version 102 and Version 103 of WKTRaster/SpecificationWorking01
- Timestamp:
- Jan 5, 2010, 2:49:59 PM (14 years ago)
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WKTRaster/SpecificationWorking01
v102 v103 265 265 This is a set-returning function (SRF). A "geomval" value is a complex type composed of a polygon geometry (one for each group of pixel sharing the same value) and the value associated with this geometry. These values are always returned as a value of type double precision. The shape of each polygon follow pixels edges. 266 266 267 Variant 1: ST_AsPolygon(raster) -> geomval set -- default to band # 1[[BR]] 268 Variant 2: ST_AsPolygon(raster, integer, 'UNGROUP')[[BR]] 269 Variant 3: ST_AsPolygon(raster, 'UNGROUP') -- default to band # 1 267 Variant 1: ST_AsPolygon(raster) -> geomval set -- default to band # 1 268 269 Variant 2: ST_AsPolygon(raster, integer, 'CONTIGUOUS')[[BR]] 270 Variant 3: ST_AsPolygon(raster, 'CONTIGUOUS') -- default to band # 1 270 271 271 272 This function should be used with precaution on raster with float pixel type as it could return one "geomval" (or polygon) per pixel. This kind of raster should be reclassified (using the planned ST_Reclassify(raster,...) function) before using ST_AsPolygon(). 272 273 273 Variant 2 splits every resulting complex polygon sharing the same value into simple (or singlepart) polygons.274 Variant 2 & 3 splits every resulting complex polygon sharing the same value into simple (or singlepart) polygons. 274 275 275 276 '''Implementation details'''