COMBINE

        COMBINE

    This  task  makes  "combinations"  of  two input  images  to  produce  a
    third  one.   The  two input images may have the same dimensions, or the
    first one (Z one) may have less dimensions than the second (Y) one.   In
    the latter case, combinations will occur for all the extra planes of the
    Y image.  For example you can divide all planes of an input (Y) 3-D cube
    by  a  2-D (Z) image, provided each plane of the cube matches the single
    image...

    Operations are
            ADD             X = Ay*Y + Az*Z + C
            MULTIPLY        X = AY*Y * AZ*Z + C
            DIVIDE          X = AY*Y / AZ*Z + C
            OPTICAL_DEPTH   X = - LOG (AY*Y / AZ*Z + C)
    provided Y > TY and Z > TZ , TY and TZ being thersholds for the Y and  Z
    images.

    Image combinations may  also  be  done  using  the  SIC  arithmetic  ca-
    pabilities,   but   COMBINE  offers  the advantage of handling correctly
    blanking information.