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.
CALL PCMPXY (IMAP,XINP,YINP,XOTP,YOTP)
#include <ncarg/ncargC.h>
void c_pcmpxy (int imap, float xinp, float yinp, float *xotp, float *yotp)
- 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
- IMAP = 2
- 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
- other < 0
-
- 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.
The C-binding argument descriptions are the same as the FORTRAN
argument descriptions.
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.
To use PCMPXY or c_pcmpxy, load the NCAR Graphics libraries ncarg,
ncarg_gks, and ncarg_c, preferably in that order.
Online: plotchar, pcdlsc, pcgetc, pcgeti, pcgetr, pchiqu, pcloqu,
pcmequ, pcpnwi, pcrset, pcsetc, pcseti, pcsetr, ncarg_cbind.
Hardcopy: NCAR Graphics Fundamentals, UNIX Version
Copyright (C) 1987-2009
University Corporation for Atmospheric Research
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