Changes between Version 20 and Version 21 of WKTRaster/SpecificationWorking02

Timestamp:

Sep 3, 2010, 2:02:09 PM (14 years ago)

Author:

pracine

Comment:

—

WKTRaster/SpecificationWorking02

@@ -15 +15 @@
 }}}
  
+----
+== '''Objective B02x - Implement better support for NULL, Empty, HasNoBand(rast), HasNoBand(rast, band) and BandIsNoData rasters in all functions.''' ==
+
+ Each function shoul better handle NULL rasters, empty rasterm rasters with no band and bands only filled with nodata values.
+
+ * 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.
+ * 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.
+ * 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.
+ * A BandIsNoData raster is a normal raster but many functions can be optimized with this type of raster.
+ * 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.
+ * Try as less as possible to return EXCEPTION (or ERROR).
+
+'''ST_IsEmpty(rast) -> boolean'''
+
+ Returns TRUE if the raster width or the raster height is 0.
+
+'''ST_HasNoBand(rast, band) -> boolean'''
+
+ Returns TRUE if the the raster does not have this band.
+
+ '''Variants'''
+
+ 1) ST_HasNoBand(rast) -> boolean
+
+ Variant 1 returns TRUE if the the raster does not have any band.
+
+'''ST_BandIsNoData(rast, band) -> boolean'''
+
+ Returns TRUE if the specified raster band is only filled with no data value.
+
+ '''Variants'''
+
+ 1) ST_BandIsNoData(rast) -> boolean
+
+ Variant 1 default to band 1.
+
+ '''Implementation details'''
+
+ This require a new flag to be set in the core at import and at edition.
+
+
 ----
 == '''Objective B02x - Being able to intersect vector and raster to produce raster.''' ==