While looking for a way to recognize text when the background color changes, I wrote the following function which calculates the ADLER checksum for an area which takes into count only the pixels of a certain color, ignoring the rest ( but it can be easily extended to compute the checksum for more that one color ) : Func PixelColorChecksum( $iColor, $iLeft, $iTop, $iRight, $iBottom ) Local Const $iMOD_ADLER = 65521 Local $iA = 1, $iB = 0, $iRow, $iCol ; Local $sStr = "" For $iRow = $iTop