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regionmanager.wmask - Function

	Package	general
	Module	images
	Tool	regionmanager

Create a world mask region

Synopsis
wmask(expr)

Arguments

expr	in	Boolean expression
		Allowed:	String

Returns
Region tool

Description

This function creates a mask region. This region can be applied on-the-fly to images. The expression must be Boolean.

Example

- im := imagemaketestimage('zz')
- r := drm.wmask(expr='zz>0')
- im.statistics(region=r)

The mask region effectively creates a (notional) Boolean lattice. In this example, when the pixel values are greater than zero, the lattice is True (good), else False. The statistics, when evaluated, are then only computed when the mask region is True.

Example

- im := imagemaketestimage('zz')
- drm.setcoordinates(im.coordsys())
#
- r1 := drm.wbox(...)                 # Make a world box
- r2 := drm.wmask(expr='zz>0')        # Make a mask region
- r3 := drm.intersection (r1,r2)      # Intersect them
- im.statistics(region=r3)            # Find statistics

In this example, the mask is only applied when the pixels fall in the specified box.