Ubuntu Manpage: PCMPXY - This routine is normally not called directly by the user (though it can be). It

NAME

       PCMPXY - This routine is normally not called directly by the user (though it can be). It
       is called by each of the routines PCHIQU, PCMEQU, and PCLOQU when the user has set the
       mapping flag ´MA´ nonzero to request mapping of characters from one X/Y coordinate system
       to another.

SYNOPSIS

       CALL PCMPXY (IMAP,XINP,YINP,XOTP,YOTP)

C-BINDING SYNOPSIS

       #include <ncarg/ncargC.h>
       void c_pcmpxy (int imap, float xinp, float yinp, float *xotp, float *yotp)

DESCRIPTION

IMAP (an input expression of type INTEGER) specifies which mapping is to be done.
Whenever Plotchar routines call PCMPXY, IMAP = ´MA´. The default version of
PCMPXY recognizes the following values of IMAP:

IMAP = 0

Type of mapping
None. When IMAP is zero, the routine PCMPXY is being asked for
information about its capabilities with respect to a particular
mapping.

XINP
Input: the real equivalent of a possible value of IMAP about which
information is desired.

YINP
Output (real): 0. says that the mapping specified by XINP is not
available, 1. that it is available, 2. that its inverse is
available, and 3. that both it and its inverse are available.

IMAP = 1

Type of mapping
Ezmap projection.

XINP
Longitude, in degrees.

YINP
Latitude, in degrees.

IMAP = 2

Type of mapping
Rho/theta mapping.

XINP
Rho, in user units.

YINP
Theta, in degrees.

IMAP = 3

Type of mapping
Projection from an arbitrary parallelogram in 3-space to an image
plane. This is implemented using a package which is currently under
development and is not yet generally available.

XINP
A multiplier for a unit vector along one edge of the parallelogram.

YINP
A multiplier for a unit vector along an intersecting edge of the
parallelogram.

IMAP = 4

Type of mapping
A version of the EZMAP projection that is intended to be used to
label specific points on the surface of the globe. When 'MA' = 4,
use "0." for each of the arguments XPOS, YPOS, and ANGD in calls to
PCHIQU and PCMEQU. Initially, each label is assumed to be placed at
the point on the globe with latitude zero and longitude zero and to
be written along the equator. Three rotations are then performed to
move the label to the point (PLAT,PLON) in such a way that it makes
an angle PANG with the local eastward-pointing vector. Finally, the
EZMAP routine MAPTRA is called to project the label as specified by
the current state of EZMAP. The desired values of PANG, PLAT, and
PLON (in degrees) are passed to PCMPXY in the labelled common block
PCMP04, which contains just those three variables, in that order.
Use the ncargex command to see the following relevant example:
cpex10.

XINP
Longitude, in degrees.

YINP
Latitude, in degrees.

IMAP = 100

Type of mapping
The identity mapping, but returns 1.E12 outside a specified
viewport. Used by the utility Scrolled_title to do clipping at the
edges of the viewport.

XINP
X coordinate, in the fractional system.

YINP
Y coordinate, in the fractional system.

other > 0

Type of mapping
The identity mapping.

XINP
Any real value.

YINP
Any real value.

other < 0

Type of mapping
An inverse mapping.

XINP
A mapped X coordinate.

YINP
A mapped Y coordinate.

Note: Values of IMAP less than or equal to zero are not currently used by
Plotchar in calling PCMPXY. The scheme described is the same as that used for
the routine CPMPXY, in the NCAR Graphics package Conpack. It is possible that,
in the future, values of IMAP less than or equal to zero will occur in calls
to PCMPXY, so it is best to be prepared.

XINP and YINP
(input expressions of type REAL) specify the X and Y coordinates of a point to
be mapped.

Note: When IMAP is less than or equal to zero (which cannot currently happen,
but may someday be possible), XINP and YINP are used differently, as shown
above.

XOTP and YOTP
(output variables of type REAL) in which PCMPXY returns the mapped X and Y
coordinates of the point. If the point is not visible under the mapping
selected (as, for example, when the orthographic projection of Ezmap is being
used and the point to be mapped is on the other side of the globe), PCMPXY
must return, as a signal that this is the case, whatever special nonzero value
has been given to the internal parameter ´OR´, so that the calling routine can
take appropriate action (to properly clip the character being drawn, for
example).

Note: When IMAP is less than or equal to zero (which cannot currently happen,
but may someday be possible), XOTP and YOTP are used differently, as shown in
the table above.

C-BINDING DESCRIPTION

       The C-binding argument descriptions are the same as the FORTRAN argument descriptions.

USAGE

       This routine is normally not called directly by the user (though it can be). It is called
       by each of the routines PCHIQU, PCMEQU, and PCLOQU when the user has set the mapping flag
       ´MA´ nonzero to request mapping of characters from one X/Y coordinate system to another. A
       call to PCMPXY has the following form:

            CALL PCMPXY (IMAP,XINP,YINP,XOTP,YOTP)

       The default version of PCMPXY does several useful mappings; a user version may be supplied
       to do others.

ACCESS

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

COPYRIGHT

       Copyright (C) 1987-2009
       University Corporation for Atmospheric Research
       The use of this Software is governed by a License Agreement.