%N xymkrd %F $MIR/src/subs/xyio.c
%D Read the masking information for an image (runs format).
%: image-i/o
%B
FORTRAN call sequence:
        subroutine xymkrd(tno,index,runs,n,nread)
        integer tno,index,n,nread
        integer runs(n)

  This reads the masking information associated with a row of an image,
  and returns it in "runs" format. 

  Input:
    tnoe        The handle associated with the image.
    index       The index of the row to determine mask info about. The
                last call to xysetpl determines which plane to access.
    n           The size of the array to receive the mask info.
  Output:
    runs        The mask info, in "runs" form. If "i" varies from 1 to
                nread/2, then pixels runs(2*i-1) to runs(2*i) are
                good, whereas pixels runs(2*i) to runs(2*i+1) are bad.
    nread       The number of "runs" read.                              
