((-idx2- (-int-)) dispi):
((-idx2- (-int-)) dispj):
((-flt-) x1 y1 x2 y2 x3 y3 x4 y4 p1 q1 p3 q3):
RETURNS: Null
SIDE EFFECTS: <dispi> <dispj>
AUTHOR: Y. LeCun
COMPILABLE: Yes
DESCRIPTION:
Tabulates a bilinear transformation that maps the quadrilateral defined
by the <xi> <yi> to a rectangle whose upper left point is <p1> <q1> and
lower right point is <p3> <q3>.
<x1> <y1> is the upper left point on the quadrilateral, and the points
are numbered clockwise.
<dispi> and <dispj> must be idx2 of int. On output, element (i,j)
of <dispi> and <dispj> will be filled respectively with the abscissa
and ordinate of the point in the quadrilateral that maps to point (i,j).
Values in these idx2 are interpreted as 32bit fixed point numbers
with 16 bit integer part and 16 bit fractional part.
<dispi> and <dispj> can subsequently be used as input to 
warp-shimage, or warp-shimage-fast.
This function makes minimal use of floating point arithmetics.