Changes between Version 253 and Version 254 of WKTRaster/SpecificationWorking03


Ignore:
Timestamp:
Jun 25, 2014, 8:07:51 PM (6 years ago)
Author:
dzwarg
Comment:

Added spec for ST_MakeEmptyCoverage

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  • WKTRaster/SpecificationWorking03

    v253 v254  
    318318 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);
    319319
     320 This method is dependent on two helper functions: ST_SetValues (see FV.23) and ST_MakeEmptyCoverage (below)
     321
    320322 Pseudo code:
    321323
     
    334336 END IF
    335337
     338'''ST_MakeEmptyCoverage(tilewidth int, tileheight int, width int, height int, upperleftx float8, upperlefty float8, scalex float8, scaley float8, skewx float8, skewy float8)'''[[BR]]
     339
     340 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.
     341
     342  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.
     343
     344  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.
     345
     346  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.
     347
     348 * Variants
     349
     350 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)
     351
     352 Variant 1 accepts an SRID parameter.
     353
    336354----
    337355== '''Objective FV.22 - Implement better support for NULL, Empty, !HasNoBand(rast), !HasNoBand(rast, band) and !BandIsNoData rasters in all functions.''' ==