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_GDIPlus_BitmapGetPixel gives me flashing window

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I use a function including _GDIPlus_BitmapGetPixel to get the pixel color from a window in the background.
I found this function somewhere on the forum and don't really know anything about GDIPlus.

Func GetColor($iX,$iY,$WinHandle)


    Local $aPos = WinGetPos($WinHandle)
    $iWidth = $aPos[2]
    $iHeight = $aPos[3]
    Local $hDDC = _WinAPI_GetDC($WinHandle)
    Local $hCDC = _WinAPI_CreateCompatibleDC($hDDC)

    $hBMP = _WinAPI_CreateCompatibleBitmap($hDDC, $iWidth, $iHeight)

    _WinAPI_SelectObject($hCDC, $hBMP)
    DllCall("User32.dll", "int", "PrintWindow", "hwnd", $WinHandle, "hwnd", $hCDC, "int", 0)
    _WinAPI_BitBlt($hCDC, 0, 0, $iWidth, $iHeight, $hDDC, 0, 0, $__SCREENCAPTURECONSTANT_SRCCOPY)

     $BMP = _GDIPlus_BitmapCreateFromHBITMAP($hBMP)
     Local $aPixelColor = _GDIPlus_BitmapGetPixel($BMP, $iX, $iY)

    _WinAPI_ReleaseDC($WinHandle, $hDDC)

    Return Hex($aPixelColor, 6)

The function is called every 200ms and works fine when the window is in the background. 
But when the window can be seen, it is heavily flashing.
Probably this is not caused by _GDIPlus_BitmapGetPixel itself, but by anything else going on in the function.

I was able to find a workaround for SOME cases by using the usual PixelGetColor whenever WinGetState tells me
the window is active (and in front). I switch to using _GDIPlus_BitmapGetPixel only when the window is inactive.
So far, so good.

But sometimes the window is inactive, but still visible, because only non-fullscreen windows are in front of it.
In this case _GDIPlus_BitmapGetPixel is used and the flashing is on.

So I either need a solution to identify this special case (inactive, but visible) or some improvement of the function
above to get rid of the flashing...

Any ideas?


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