等值线函数.// As this code is ported from FORTRAN-77, please be very careful of the // various indices like ilb,iub,jlb and jub, remeber that C/C++ indices // starts from zero (0)-contour function. / / As this code is ported from FORTRAN-77, please be very careful of the / / various indices like ilb, iub, and * address, remember that the C / C indices / / starts from zero (0)