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regionmanager.extension - Function

	Package	general
	Module	images
	Tool	regionmanager

Extend a world region to extra dimensions

Synopsis
extension(box, region, comment)

Arguments

box	in	The world region to extend over
		Allowed:	World box region tool
region	in	The world region to extend
		Allowed:	Region tool
comment	in	A comment stored with the region
		Allowed:	String

Returns
Region tool or fail

Description

This function (short-hand name ext) creates a region which is the extension over specified dimensions along straight lines of the given region. For example, you might like to extend a 2-D polygon to be a 3-D `cylindrical polygon' (that is, the polygon is replicated for each plane).

The extension is specified with a world box. It can be of any dimension. However, you can't put the same axes in the extension box as are in the region you are extending.

Example

- im := image('cube')
- cs := im.coordsys()
- im.shape()
[155 178 64]  
-
- drm.setcoordinates(cs)
-
- x := dq.quantity([40,45,48,55,48,43,40], 'pix')
- y := dq.quantity([40,43,59,60,53,48,45], 'pix')
- poly := drm.wpolygon(x, y, [1,3])
- box := drm.wbox(dq.quantity("20pix"), dq.quantity("30pix"), [2])
- 
- ext := drm.extension(box, poly, 'a cylindrical polygon')
-
- im.boundingbox(poly)
[blc=[40 1 40] , trc=[55 178 60] , inc=[1 1 1] , bbShape=[16 178 21] ,
regionShape=[16 178 21] , imageShape=[155 178 256] ] 
-
- im.boundingbox(box)
[blc=[1 20 1] , trc=[155 30 256] , inc=[1 1 1] , bbShape=[155 11 256] ,
regionShape=[155 11 256] , imageShape=[155 178 256] ]
-
- im.boundingbox(ext)
[blc=[40 20 40] , trc=[55 30 60] , inc=[1 1 1] , bbShape=[16 11 21] ,
regionShape=[16 11 21] , imageShape=[155 178 256] ]

In this example we create a 2D polygon in the XZ plane. We then create a 1D box along the Y axis from pixels 20 to 30. Then we extend the polygon with that box to make a series of XZ polygons for the specified Y pixels.

Note that when the box and poly regions are applied to the image with the boundingbox function, the auto-extension operation is applied. It is not until the region has as many dimensions as the image (the region ext) that no auto-extension occurs.