#include <GDIPlus.au3>

Global $sImagefile = @ScriptDir & '\test.jpg'

_GDIPlus_Startup()
Global $hImage = _GDIPlus_BitmapCreateFromFile($sImagefile)
$iTimer = TimerInit()
$iCount = _GetUniqueColors($hImage)
ConsoleWrite('Zeit: ' & Int(TimerDiff($iTimer)) & ' ms' & @CR)
ConsoleWrite('Anzahl der Farben: ' & $iCount & @CR)
_GDIPlus_BitmapDispose($hImage)
_GDIPlus_Shutdown()
Exit

Func _GetUniqueColors(ByRef $hImage)
	Local $iW, $iH, $tBitmapData, $pScan0, $tPixel, $iOffset, $iColor, $oUnique = ObjCreate('Scripting.Dictionary')
	$iW = _GDIPlus_ImageGetWidth($hImage)
	$iH = _GDIPlus_ImageGetHeight($hImage)
	$tBitmapData = _GDIPlus_BitmapLockBits($hImage, 0, 0, $iW, $iH, $GDIP_ILMREAD, $GDIP_PXF32ARGB)
	$pScan0 = DllStructGetData($tBitmapData, 'Scan0')
	$tPixel = DllStructCreate('uint[' & $iW * $iH & '];', $pScan0)
	ConsoleWrite('$iW * $iH = ' & $iW * $iH & ' px' & @CRLF)
	For $iY = 0 To $iH - 1
		$iOffset = $iY * $iW + 1
		For $iX = 0 To $iW - 1
			$iColor = Hex(DllStructGetData($tPixel, 1, $iOffset + $iX), 8)
			$oUnique.Item($iColor) = 0
		Next
	Next
	_GDIPlus_BitmapUnlockBits($hImage, $tBitmapData)
	$tPixel = 0
	Return $oUnique.Count
EndFunc