[postgis-tickets] [PostGIS] #2210: [raster]: ST_Envelope for raster that considers only data values

[PostGIS]

#2210: [raster]: ST_Envelope for raster that considers only data values
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 Reporter:  robe         |       Owner:  dustymugs     
     Type:  enhancement  |      Status:  new           
 Priority:  medium       |   Milestone:  PostGIS Future
Component:  raster       |     Version:  trunk         
 Keywords:               |  
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 This would be like our current ST_Envelop (we could add an optional arg).
 This would essentially return the envelop of a raster not considering no
 data values.

 We can do this now with ST_Envelope(ST_Polygon ..) but that process is
 slow because it has to consider all pixels.  This one wouldn't need to
 consider all pixels because it would start at the outer perimeter,
 collapse inward and stop checking once it hit a pixel with data, since the
 envelop can't get any smaller.

 In dustymug's words:

 We're looking for a boundary function rather than a polygon function
 (which includes holes for interior NODATA pixels). I'm looking for less
 than that -- since I still expect it to be a rectangle, not a concave hull

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/2210>
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