function GetFloodFillMask(img: TImage32; x, y: Integer; compareFunc: TCompareFunction; tolerance: Integer): TArrayOfByte;

Starting at pixel (x,y), the floodfill algorithm progresses to adjacent pixels whose colors match the start pixel's color according to the supplied compare function. The returned mask is a binary (true/false) unidimensional array whose length corresponds to the supplied image's width x height.