PixelChecksum not working correctly, tried PixelCoordMode options

[ribo75016]

Hello,

I'm using an i7 6700T CPU with internal Intel 530 GPU

And this piece of code:

HotKeySet("{F8}", "F8")

Func F8()

;Opt("PixelCoordMode", 2) ; Tried 0 1 and 2 without significant differences
Local $tmp = MouseGetPos()
Local $Checksum = PixelChecksum($tmp[0], $tmp[1], $tmp[0] + 50, $tmp[1] + 50)
MsgBox(0, "Cksum", $tmp[0] & '/' & $tmp[1] & '/' & $tmp[0] + 50 & '/' & $tmp[1] + 50 & '/' & $Checksum)

EndFunc

While (1)

Sleep(100)

Wend

Checksum is often same value (only coord is modified), whereas I move the mouse cursor on different texts.

I've already used PixelChecksum without any problem before but with an 'external'  graphic card

Regards,
Philippe