AH = 0Dh: Read Graphics Pixel

This function returns the value of the specified pixel. The range of valid pixel (x,y) addresses depends on the video mode.

• Input: AH = 0Dh
  BH = Page (not used by HP 100LX)
  CX = x (Column or Horizontal pixel address)
  DX = y (Row or Vertical pixel address)
  

• Output: AL = Pixel Value (0 or 1 in hi-res, or 0-3 in lo-res)
• Error conditions: None
• Registers modified: AX