ncl_hafton - Man Page

This routine is part of the Halftone utility in NCAR Graphics. To see the overview man page for this utility, type "man halftone".

HAFTON is obsolete.  It has been replaced by the CPCICA entry of the Conpack contouring package.

HAFTON continues to be provided for compatibility of early NCAR Graphics codes.  If you are writing new code, we suggest that you use CPCICA.

CALL HAFTON (Z,L,M,N,FLO,HI,NLEV,NOPT,NPRM,ISPV,SPVAL)

Z

(an input array of type REAL) defining a two-dimensional field to be half-tone plotted. A subset of Z of extent M by N can be plotted.

L

(an input parameter of type INTEGER) which is the first dimension of the Z array.

M

(an input parameter of type INTEGER) which is the extent of the first dimension of array Z to be plotted.  This allows for a sub-array of Z to be plotted.  M must be less than or equal to L.

N

(an input parameter of type INTEGER) which is the extent of the second dimension of array Z to be plotted.  This allows for a sub-array of Z to be plotted.  N must be less than or equal to the second dimension of Z.

FLO

(an input parameter of type REAL) defining a lowest level for plotting. If FLO = HI = 0., the minimum value of Z will be generated by HAFTON.

HI

(an input parameter of type REAL) defining a highest level for plotting. If HI = FLO = 0., the maximum value of Z will be generated by HAFTON.

NLEL

(an input parameter of type INTEGER) specifying the number of intensity levels desired.  16 maximum.  If NLEV = 0 or 1, 16 levels are used.

NOPT

(an input parameter of type INTEGER) used to control the mapping of Z onto the intensities.  The sign of NOPT controls the directness or inverseness of the mapping.

NOPT positive yields direct mapping. The largest value of Z produces the most dense dots.  On mechanical plotters, large values of Z will produce a dark area on the paper.  With the film development methods used at NCAR, large values of Z will produce many (white) dots on the film, also resulting in a dark area on reader-printer paper.

NOPT negative yields inverse mapping. The smallest values of Z produce the most dense dots resulting in dark areas on the paper.

The absolute value of NOPT determines the mapping of Z onto the intensities.  For IABS(NOPT)

= 0  The mapping is linear.  For
    each intensity there is an equal
    range in Z value.

= 1  The mapping is linear.  For
    each intensity there is an equal
    range in Z value.

= 2  The mapping is exponential.  For
    larger values of Z, there is a
    larger difference in intensity for
    relatively close values of Z.  Details
    in the larger values of Z are displayed
    at the expense of the smaller values
    of Z.

= 3  The mapping is logarithmic, so
    details of smaller values of Z are show
    at the expense of larger values of Z.

= 4  Sinusoidal mapping, so mid-range values
    of Z show details at the expense of
    extreme values of Z.

= 5  Arcsine mapping, so extreme values of
    Z are shown at the expense of mid-range

NPRM

(an input parameter of type INTEGER) used to control the drawing of a perimeter around the half-tone picture.

NPRM=0:  The perimeter is drawn with ticks pointing at data locations. (Side lengths are proportional to number of data values.)

NPRM positive:  No perimeter is drawn.  The picture fills the frame.

NPRM negative:  The picture is within the confines of the user's current viewport setting.

ISPV

(an input parameter of type INTEGER) used to tell if the special value feature is being used.  The special value feature is used to mark areas where the data is not known or holes are wanted in the picture.

ISPV = 0:  Special value feature not in use.  SPVAL is ignored.

ISPV non-zero:  Special value feature in use.  SPVAL defines the special value.  Where Z contains the special value, no half-tone is drawn.  If ISPV

= 0  Special value feature not in use.
    SPVAL is ignored.

= 1  Nothing is drawn in special value
    area.

= 2  Contiguous special value areas are
    surrounded by a polygonal line.

= 3  Special value areas are filled
    with X(s).

= 4  Special value areas are filled in
    with the highest intensity.

SPVAL

(an iput parameter of type REAL) used to denote missing values in the Z array. This argument is ignored if ISPV = 0.

To use HAFTON, load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in that order.

Online: halftone, ezhftn, halftone_params, conpack, conpack_params, cpcica

Hardcopy:   NCAR Graphics Contouring and Mapping Tutorial; NCAR Graphics Fundamentals, UNIX Version; User's Guide for NCAR GKS-0A Graphics

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