%N pgconf %F $MIR/src/pgconf.f
%D Fill between two contours
%B
      SUBROUTINE PGCONF (A, IDIM, JDIM, I1, I2, J1, J2, C1, C2, TR)
      INTEGER IDIM, JDIM, I1, I2, J1, J2
      REAL    A(IDIM,JDIM), C1, C2, TR(6)

 Shade the region between two contour levels of a function defined on
 the nodes of a rectangular grid. The routine uses the current fill
 attributes, hatching style (if appropriate), and color index.

 If you want to both shade between contours and draw the contour
 lines, call this routine first (once for each pair of levels) and 
 then CALL PGCONT (or PGCONS) to draw the contour lines on top of the
 shading.

 Note 1: This routine is not very efficient: it generates a polygon
 fill command for each cell of the mesh that intersects the desired
 area, rather than consolidating adjacent cells into a single polygon.

 Note 2: If both contours intersect all four edges of a particular
 mesh cell, the program behaves badly and may consider some parts
 of the cell to lie in more than one contour range.

 Note 3: If a contour crosses all four edges of a cell, this
 routine may not generate the same contours as PGCONT or PGCONS
 (these two routines may not agree either). Such cases are always
 ambiguous and the routines use different approaches to resolving
 the ambiguity.

 Arguments:
  A      (input)  : data array.
  IDIM   (input)  : first dimension of A.
  JDIM   (input)  : second dimension of A.
  I1,I2  (input)  : range of first index to be contoured (inclusive).
  J1,J2  (input)  : range of second index to be contoured (inclusive).
  C1, C2 (input)  : contour levels; note that C1 must be less than C2.
  TR     (input)  : array defining a transformation between the I,J
                    grid of the array and the world coordinates. The
                    world coordinates of the array point A(I,J) are
                    given by:
                      X = TR(1) + TR(2)*I + TR(3)*J
                      Y = TR(4) + TR(5)*I + TR(6)*J
                    Usually TR(3) and TR(5) are zero - unless the
                    coordinate transformation involves a rotation
                    or shear.
