INT 10h,  0Dh (13)       Read Pixel

    Reports the color of the pixel at a specified screen coordinate.

       On entry:      AH         0Dh
                      CX         Horizontal position of pixel
                      DX         Vertical position of pixel
                      BH         Display page number (graphics modes with more
                                 than 1 page)

       Returns:       AL         Color of pixel

       Registers destroyed:      AX, SP, BP, SI, DI

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                             Legal values

  Mode   CX (Horizontal)  DX (Vertical)   AL (Pixel Color)    BH (Page Number)
   04h      0-319            0-199             0-3
   05h       0-319            0-199             0-3
   06h       0-639            0-199             0-1
   0Dh       0-319            0-199             0-15                  0-7
   0Eh       0-639            0-199             0-15                  0-3
   0Fh       0-639            0-349             0-1                   0-1
   10h       0-639            0-349             0-15                  0-1
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       Notes:         For modes 0Dh through 10h, a page number needs to be
                      supplied in BH.