There are a couple places where FileSetTime() can have an error and return without restoring the original working directory. It's obvious from looking at the code where this is.

The documentation on operators should specify if they are case-sensitive or not when applied to 2 string arguments.

<> , < , > , <= , >= are case insensitive

is already specified as case insensitive

is already specified as case sensitive

Beginners should be warned that the negation of the condition (A == B) is the condition (Not (A == B)) which is different from A <> B).

_GDIPlus_BitmapUnlockBits dose not release the allocated memory. If you change the DllCall-type "int*" to "ptr" it works fine - see example:

#include <ScreenCapture.au3>

Global $hScreen, $hBitmap, $aMem, $tData

_GDIPlus_Startup()
$hScreen=_ScreenCapture_Capture("", 0, 0, -1, -1, False)
$hBitmap = _GDIPlus_BitmapCreateFromHBITMAP($hScreen)

For $i=1 To 50
    $tData = _GDIPlus_BitmapLockBits($hBitmap, 0, 0, _GDIPlus_ImageGetWidth($hBitmap), _GDIPlus_ImageGetHeight($hBitmap), $GDIP_ILMREAD, $GDIP_PXF24RGB)
    _GDIPlus_BitmapUnlockBits($hBitmap, $tData)
    Sleep(50)
    $aMem = MemGetStats()
    ConsoleWrite("original function; step " & $i & "; mem usage: " & $aMem[0] & @LF)
Next

ConsoleWrite(@LF)

For $i=1 To 50
    $tData = _GDIPlus_BitmapLockBits($hBitmap, 0, 0, _GDIPlus_ImageGetWidth($hBitmap), _GDIPlus_ImageGetHeight($hBitmap), $GDIP_ILMREAD, $GDIP_PXF24RGB)
    _GDIPlus_BitmapUnlockBits_($hBitmap, $tData)
    Sleep(50)
    $aMem = MemGetStats()
    ConsoleWrite("test function; step " & $i & "; mem usage: " & $aMem[0] & @LF)
Next

Func _GDIPlus_BitmapUnlockBits_($hBitmap, $tBitmapData)
    Local $aResult

    $aResult = DllCall($ghGDIPDll, "int", "GdipBitmapUnlockBits", "hwnd", $hBitmap, "ptr", DllStructGetPtr($tBitmapData)) ;Type ptr instead of int*
    If @error Then Return SetError(@error, @extended, False)
    Return SetError($aResult[0], 0, $aResult[0] = 0)
EndFunc   ;==>_GDIPlus_BitmapUnlockBits