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regionmanager.intersection - Function

1.1.2 Create the intersection of some world regions


Description

This function (short-hand name int) creates a region which is the intersection of the given world regions. The input regions can themselves be compound regions (such as the union or intersection etc). The input regions must be provided as a Python dictionary of regions (see examples).

Arguments





Inputs

regions

World regions and comment

allowed:

any

Default:

variant

Region tools or record of region tools, and String

comment

A comment stored with the region

allowed:

string

Default:

String

Returns
record

Example

 
 
- ia.open(’hcn’)  
- csys = ia.coordsys()  
- rg.setcoordinates(csys.torecord())  
-  
- blc = "10pix 10pix 1pix"  
- trc = "60pix 60pix 1pix"  
- r1 = rg.wbox(blc=blc, trc=trc, pixelaxes=[0,1,2])  
-  
- x = qa.quantity([50,55,58,65,58,53,50], ’pix’)  
- y = qa.quantity([50,53,69,70,63,58,55], ’pix’)  
- r2 = rg.wpolygon(x=x, y=y, pixelaxes=[0,1])  
-  
- regions= {’region1’:r1, ’region2’:r2}  
- r3 = rg.intersection(regions, ’This is the comment’)  
-  
- ia.boundingbox(r1)  
[blc=[10 10 1] , trc=[60 60 256] , regionShape=[51 51 256] , imageShape=[155 178 256] ]  
- ia.boundingbox(r2)  
[blc=[50 50 1] , trc=[65 70 256] , regionShape=[16 21 256] , imageShape=[155 178 256] ]  
- ia.boundingbox(r3)  
[blc=[50 50 1] , trc=[60 60 256] , regionShape=[11 11 256] , imageShape=[155 178 256] ]  
-  
- ia.statistics(region=r3)                           # Some output discarded  
NORMAL: Selected bounding box [50, 50, 1] to [60, 60, 1]  
Number points = 51  
 
 
 
In this example, we use pixel coordinates so that it is clear what is  
happening.  You can see that the number of pixels in the intersection  
(51) is less than the number in the bounding box of the intersection  
(121) because the intersection is actually polygonal and does not fill  
the bounding box.  
 

Example

 
 
- ia.open(’onno’)  
- csys = ia.coordsys()  
- x = qa.quantity([3,6,9,6,5,5,3],’pix’)  
- y = qa.quantity([3,4,7,9,7,5,5],’pix’)  
-  
- regions = {};  
- regions[’poly’] = rg.wpoly(x,y,[1,2],csys.torecord())  
-  
- blc = "17:42:29.303 -28.59.18.600"  
- trc = "17:42:28.303 -28.59.10.600"  
- regions[’box’] = rg.wbox(blc,trc,[0,1],csys.torecord())  
-  
- r3 = rg.intersection(regions,’The mysteries of CASA’)  
 
 
This example is the same as the prevoius one, except the regions are  
provided to the intersection function in a record, rather than directly in the  
call sequence.  
 

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