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image.pbcor - Function

1.1.1 Construct a primary beam corrected image from an image and a primary beam


Description

Correct an image for primary beam attenuation using an image of the primary beam pattern. The primary beam pattern can be provided as an image, in which case 1. it must have the same shape as the input image and its coordinate system must be the same, or 2. it must be a 2-D image in which case its coordinate system must consist of a (2-D) direction coordinate which is the same as the direction coordinate in the input image and its direction plane must be the same shape as that of the input image. Alternatively, pbimage can be an array of pixel values in which case the same dimensionality and shape constraints apply. An image tool referencing the corrected image is returned. The corrected image will also be written to disk if outfile is not empty (and overwrite=True if outfile already exists). One can choose between dividing the image by the primary beam pattern (mode=”divide”) or multiplying the image by the primary beam pattern (mode=”multiply”). One can also choose to specify a cutoff limit for the primary beam pattern. For mode=”divide”, for all pixels below this cutoff in the primary beam pattern, the output image will be masked. In the case of mode=”multiply”, all pixels in the output will be masked corresponding to pixels with values greater than the cutoff in the primary beam pattern. A negative value for cutoff means that no cutoff will be applied, which is the default.

Arguments

Inputs

pbimage

Name of the primary beam image which must exist or array of values for the pb response. Default ””

allowed:

any

Default:

variant

outfile

Output image name. If empty, no image is written. Default ””

allowed:

string

Default:

overwrite

Overwrite the output if it exists? Default False

allowed:

bool

Default:

false
box

Rectangular region(s) to select in direction plane. See ”help par.box” for details. Default is to use the entire direction plane.

allowed:

string

Default:

region

Region selection. See ”help par.region” for details. Default is to use the full image.

allowed:

any

Default:

variant

chans

Channels to use. See ”help par.chans” for details. Default is to use all channels.

allowed:

string

Default:

stokes

Stokes planes to use. See ”help par.stokes” for details. Default is to use all stokes planes.

allowed:

string

Default:

mask

Mask to use. See help par.mask. Default is none.

allowed:

string

Default:

variant

mode

Divide or multiply the image by the primary beam image. Minimal match supported. Default ”divide”

allowed:

string

Default:

divide

cutoff

PB cutoff. If mode is ”d”, all values less than this will be masked. If ”m”, all values greater will be masked. Less than 0, no cutoff. Default no cutoff

allowed:

float

Default:

-1.0

stretch

Stretch the mask if necessary and possible? See help par.stretch. Default False

allowed:

bool

Default:

false

Returns
image

Example

 
        ia.open("attenuated.im")  
        pbia = ia.pbcor(pbimage="mypb.im", outname="pbcorred.im", mode="divide", cutoff=0.1)  
        ia.done()  
        # do stuff with ia tool attached to pb image and close it  
        pbia.done()  

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