Description
A mask image is an image with the same shape as the other images but
with values between 0.0 and 1.0 as a pixel value. Mask images are used
in
imager to control the region selected in a deconvolution.
One makes a mask image by clipping the I part of the restored image
(this function) or via the
boxmask,
regionmask, and
exprmask functions. In this
function, all points greater than the threshold are set to unity. The
mask is the same in I,Q,U, and V. Note that
exprmask is the most powerful
method for making mask images.
In the Clark CLEAN, the mask image can usefully have any value between
0.0 and 1.0. Intermediate value discourage but do not rule out
selection of clean components in that region. This is accomplished by
multiplying the residual image by the mask prior to entering the minor
cycle.
Note that if you do use a mask for the Clark or Hogbom Clean, it must
cover only a quarter of the image. It is particularly important to
check this when creating an image using a threshold. If it extends
further, the easiest fix is to use
getchunk and
getchunk to set parts of it to zero.
Arguments
| image |
in |
name of template image |
|
|
Allowed: |
String |
| mask |
in |
name of mask image |
|
|
Allowed: |
String |
| threshold |
in |
threshold for mask |
|
|
Allowed: |
Quantity |
|
|
Default: |
'0.0Jy' |
| async |
in |
Run asynchronously in the background |
|
|
Allowed: |
Bool |
|
|
Default: |
!dowait |
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