Changes between Version 20 and Version 21 of WKTRaster/SpecificationWorking02


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Timestamp:
Sep 3, 2010, 2:02:09 PM (10 years ago)
Author:
pracine
Comment:

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  • WKTRaster/SpecificationWorking02

    v20 v21  
    1515}}}
    1616 
     17----
     18== '''Objective B02x - Implement better support for NULL, Empty, HasNoBand(rast), HasNoBand(rast, band) and BandIsNoData rasters in all functions.''' ==
     19
     20 Each function shoul better handle NULL rasters, empty rasterm rasters with no band and bands only filled with nodata values.
     21
     22 * Generally, when NULL rasters are provided, return NULL. If the function involves a second non NULL raster and something can be done with it, do it.
     23 * Generally, when empty rasters are provided (ST_IsEmpty, width=0 or height=0), return an empty raster. If the function involves a second non empty raster and something can be done with it, do it.
     24 * Generally, when a HasNoBand(rast) or a HasNoBand(rast, band) raster is provided return a raster with no band but with the right extent. If the function involves a second raster having a band or the band, treat the first missing band like a BandIsNoData.
     25 * A BandIsNoData raster is a normal raster but many functions can be optimized with this type of raster.
     26 * All functions having missing the requested information (about its extent when it is a NULL or an empty raster or about its band when it is a HasNoBand(rast) or a HasNoBand(rast, band) raster) should return NULL or a documented value.
     27 * Try as less as possible to return EXCEPTION (or ERROR).
     28
     29'''ST_IsEmpty(rast) -> boolean'''
     30
     31 Returns TRUE if the raster width or the raster height is 0.
     32
     33'''ST_HasNoBand(rast, band) -> boolean'''
     34
     35 Returns TRUE if the the raster does not have this band.
     36
     37 '''Variants'''
     38
     39 1) ST_HasNoBand(rast) -> boolean
     40
     41 Variant 1 returns TRUE if the the raster does not have any band.
     42
     43'''ST_BandIsNoData(rast, band) -> boolean'''
     44
     45 Returns TRUE if the specified raster band is only filled with no data value.
     46
     47 '''Variants'''
     48
     49 1) ST_BandIsNoData(rast) -> boolean
     50
     51 Variant 1 default to band 1.
     52
     53 '''Implementation details'''
     54
     55 This require a new flag to be set in the core at import and at edition.
     56
     57
    1758----
    1859== '''Objective B02x - Being able to intersect vector and raster to produce raster.''' ==