The DRHD chunk contains the upper left and lower right extremes of the
document in (X, Y) coordinates.  This chunk is required and should
only appear once in a document in the outermost layer of the DR2D file
(DR2Ds can be nested).

    struct DRHDstruct {
        ULONG       ID;
        ULONG       Size;                   /* Always 16 */
        IEEE        XLeft, YTop,
                    XRight, YBot;
    };

The point (XLeft,YTop) is the upper left corner of the project and the
point (XRight,YBot) is its lower right corner.  These coordinates not
only supply the size and position of the document in a coordinate
system, they also supply the project's orientation.  If XLeft <
XRight, the X-axis increases toward the right.  If YTop < YBot, the
Y-axis increases toward the bottom.  Other combinations are possible;
for example in Cartesian coordinates, XLeft would be less than XRight
but YTop would be greater than YBot.