Documentation on immask

Task: immask
Purpose: Mask an image dataset
Categories: image analysis

   IMMASK is a MIRIAD task which allows you to mask an image
   dataset.  

   Masking is directly done to the ``mask'' item of an image dataset, 
   the program does not have to copy data, but modifies it ``in situ''. 
   The actual image data themselves (the ``image'' item) are not 
   modified, only the mask; so a final word of relief: to reset all
   pixels to their original value:
       delhd in=IMAGE/mask
   for any ``IMAGE'' dataset.
   To set all pixels in the dataset to FALSE:
       immask in=IMAGE flag=false logic=and

   See also MATHS for other ways to set the image mask.

Key: in
   The name of the input image dataset. No default.

Key: region
   Regions which will be masked with the ``flag'' value (see below).
   Full region descriptions are supported.
   Note that missing image planes will then be automatically masked 
   to the opposite value set by the ``flag'' keyword below. 
   Default: whole image.

Key: logic
   The logic of the masking operation. It can have a value of ``AND'',
   `OR'' or ``NOT'' which determines how the selected region(s) from the 
   region= keyword are masked with the existing mask item in the image:
       OR:     region .OR. mask
       AND:    region .AND. mask
       NOT:    if (region) .NOT.mask
   If no value provided, the program will simply report on the 
   total number of pixels flagged good and bad.
   No default.

Key: flag
   The value of the mask inside the selected regions. Can be ``true''
   or ``false''. Outside selected region it will be its opposite.
   A ``true'' value is considerd a good pixel.
   Default: true.

Key: history
   Logical, denoting if the history should be updated. This should
   normally never be set to false, though some scripts prefer
   to do this manually via ADDHIS, and set this parameter to FALSE.
   In reporting mode (no ``logic'' operation supplied) the history
   is not updated.
   Default: TRUE

Key: options
   Valid options: 
      datamin      flag all values with `flag' when data is datamin
   Default: none.