[postgis-devel] [PostGIS] #903: [raster] ST_Reclass

[PostGIS]

#903: [raster] ST_Reclass
----------------------------+-----------------------------------------------
 Reporter:  dustymugs       |       Owner:  dustymugs            
     Type:  task            |      Status:  assigned             
 Priority:  medium          |   Milestone:  PostGIS Raster Future
Component:  postgis raster  |     Version:  trunk                
 Keywords:                  |  
----------------------------+-----------------------------------------------

Comment(by dustymugs):

 In writing ST_Reclass, I noticed there was an inherent weakness regarding
 the user defining a nodata value for the reclassified band.  As such, I
 believe the new type "reclassarg" needs to be expanded:

 {{{
 CREATE TYPE reclassarg AS (
   nband int,
   reclassexpr text,
   pixeltype text,
   nodataval double precision
 );
 }}}

 By specifying a nodata value, ST_Reclass can automatically existing nodata
 values to the new nodata value and allows the reclassexpr to convert other
 values to the nodata value.

 Also, ST_Reclass should have several variations.

 1. ST_Reclass(rast raster, VARIADIC reclassargset reclassarg[])

   The default function

 2. ST_Reclass(rast raster, nband int, reclassexpr text, pixeltype text,
 nodataval double precision)

   Convert a single band instead of a set of parameters rather than using
 reclassarg

 {{{
 ST_Reclass(rast, 1, '0-100:1-10, 101-500:11-150,501 - 10000: 151-254',
 '8BUI', 255)
 }}}

 3. ST_Reclass(rast raster, nband int, reclassexpr text, pixeltype text)

   New band has no nodata value unlike in !#2

 {{{
 ST_Reclass(rast, 1, '0-100:1-10, 101-500:11-150,501 - 10000: 151-254',
 '8BUI')
 }}}

 4. ST_Reclass(rast raster, reclassexpr text, pixeltype text)

   Assume band index is 1 and has no nodata value

 {{{
 ST_Reclass(rast, '0-100:1-10, 101-500:11-150,501 - 10000: 151-254',
 '8BUI')
 }}}

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/903#comment:10>
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