INT 62 u - FGDRIVER v3.03 - "FG_GETBLOCK" - GRAB RECTANGLE OF DISPLAY
        AX = 0031h
        ES:BX -> buffer for screen contents
        CX = leftmost column
        DX = rightmost column
        SI = top row
        DI = bottom row
Notes:  For FGDRIVER v1.10, this function was unused, and "FG_GETBLOCK" did not
          exist yet
        In text modes, coordinates are character positions; in graphics modes,
          they are defined in screen space, and the left and right edges are
          adjusted to a byte boundary if necessary
        Use "FG_IMAGESIZ" (see AX=004Bh) to determine the required buffer size
SeeAlso: AX=0038h,AX=004Bh,AX=007Dh

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