Documentation on avmaths

Task: avmaths
Purpose: Operate on cube with averaged plane from cube
Categories: analysis

        AVMATHS averages designated planes from a cube, and then 
        performs some mathematical operation on the cube with the 
        averaged plane. Currently subtraction, optical depth, and
        replacement operations have been coded.  Undefined output
        pixels are blanked.

Key: in
        The input image. Wild card expansion is supported. No default.

Key: out
        The output image. No default.

Key: region
        Specify the channels to average with a REGION=IMAGE
        command such as
          region=image(1,5),image(120,128)
        This would average channels 1:5 and 120:128 from the
        cube.  No other region commands are accepted for example
        spatial sub-regions will be ignored.

Key: options
        Task enrichment options.  Minimum match is active.

        "subtract" for subtraction:   OUT(i,j,k) = IN(i,j,k) - AV(i,j)
        "odepth"   for optical depth: OUT(i,j,k) = LN (AV(i,j) / IN(i,j,k))
        "replace"  for replacement:   OUT(i,j) = AV(i,j)
        "multiply" for multiplication OUT(i,j,k) = IN(i,j,k) * AV(i,j)

        "noreduce" causes the output image to be of the same dimensions
            as the input image when REPLACEMENT is invoked.  By default,
            the REPLACED output image is reduced to two dimensions as
            there is probably no point to replicating one plane N times.
            In this case, the output third axis descriptors reflect the size
            of the bounding box of the selected region on the third axis

        Pixels are blanked if the input pixel is blanked, the averaged
        channel pixel is blanked, or the output is undefined.