Changes between Version 253 and Version 254 of WKTRaster/SpecificationWorking03

Timestamp:

Jun 25, 2014, 8:07:51 PM (10 years ago)

Author:

dzwarg

Comment:

Added spec for ST_MakeEmptyCoverage

WKTRaster/SpecificationWorking03

@@ -318 +318 @@
  Creates the tiles corresponding to the lower resolution (or overviews) of a raster table. So that an overview table can be created like this: SELECT ST_CreateOverviews(rasttable, rast, 2);
 
+ This method is dependent on two helper functions: ST_SetValues (see FV.23) and ST_MakeEmptyCoverage (below)
+
  Pseudo code:
 
@@ -334 +336 @@
  END IF
 
+'''ST_MakeEmptyCoverage(tilewidth int, tileheight int, width int, height int, upperleftx float8, upperlefty float8, scalex float8, scaley float8, skewx float8, skewy float8)'''[[BR]]
+
+ Creates a set of rasters that regularly cover the area described by the coordinates. The net coverage of the returned set of rasters is the contiguous coverage over the area described by the coordinates. Each individual raster in the set will have all pixel values set to NODATA.
+
+  If the width of the empty coverage is not a multiple of the tilewidth, then the empty coverage will contain rasters on the right (highest upperleftx value) that are "thinner": they will be (width - (tilewidth * (width % tilewidth))) wide.
+
+  If the height of the empty coverage is not a multiple of the tileheight, then the empty coverage will contain rasters on the bottom (lowest upperlefty value) that are "shorter": they will be (height - (tileheight * (height % tileheight))) tall.
+
+  If the width and height are not multiples of tilewidth and tileheight, respectively, then the empty coverage will contain one raster at the bottom right corner (highest upperleftx value, lowest upperlefty value) that is both "thinner" and "shorter" by the calculations above for width and height, respectively.
+
+ * Variants
+
+ 1) ST_MakeEmptyCoverage(tilewidth int, tileheight int, width int, height int, upperleftx float8, upperlefty float8, scalex float8, scaley float8, skewx float8, skewy float8, srid int4)
+
+ Variant 1 accepts an SRID parameter.
+
 ----
 == '''Objective FV.22 - Implement better support for NULL, Empty, !HasNoBand(rast), !HasNoBand(rast, band) and !BandIsNoData rasters in all functions.''' ==