# ncl_hafton - Man Page

draws a half-tone picture from data stored in a rectangular array with the intensity in the picture proportional to the data value.

## Utility

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

## Status

HAFTON is obsolete. It has been replaced by the CPCICA entry of the Conpack contouring package.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

## Synopsis

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

## Description

- 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.

## Access

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

## See Also

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

## Copyright

Copyright (C) 1987-2009

University Corporation for Atmospheric Research

The use of this Software is governed by a License Agreement.