begin
MemStream := TMemoryStream.Create;
try
Bmp1.SaveToStream(MemStream);
MemStream.Position := 0;
SetLength(S1, MemStream.Size);
MemStream.Read(S1[1], Length(S1));
MemStream.Clear;
Bmp2.SaveToStream(MemStream);
MemStream.Position := 0;
SetLength(S2, MemStream.Size);
MemStream.Read(S2[1], Length(S2));
finally
MemStream.Free;
end;
if S1 = S2 then
{they are identically};
end;