Programming with VisionX File FunctionsVisionX programs that are developed with the structured VisionX programming tools usually have the following structure:
A basic VisionX program that illustrates all the main features of the structured VisionX programming tools is shown in Figure 1. Since this structure is similar for most VisionX programs, the example program may be used as a template for developing other programs. Figure 1: Template VisionX Program
/****************************************************************/
/* Example VisX4 program vcp -- Copy a VisX data file */
/* Syntax: */
/* vcp [-f] if=infile of=outfile */
/****************************************************************/
#include "VisXV4.h" /* VisX structure include file */
#include "Vutil.h" /* useful macros, stdio.h etc. */
/* */
VisXfile_t *VXin, /* input file structure */
*VXout; /* output file structure */
VisXelem_t *vxlist; /* VisX data structure */
/* */
VXparam_t par[] = /* command line structure */
{
{ "if=", 0, "input file vcp: file copy"},
{ "of=", 0, "output file"},
{ "-f", 0, "frame-i/o option"},
{ 0, 0, 0}, /* list termination */
};
#define IVAL par[0].val
#define OVAL par[1].val
#define FFLAG par[2].val
main(argc, argv)
int argc;
char *argv[];
{
VXparse(&argc, &argv, par); /* parse the command line */
VXin = VXopen(IVAL, 0); /* open input file */
VXout = VXopen(OVAL, 1); /* open the output file */
if(!FFLAG){ /* do complete file i/o */
vxlist = VXread(VXin); /* read data */
VXwrite(VXout, vxlist); /* write data */
}else { /* do frame i/o */
while ((vxlist = VXreadframe(VXin)) != VXNIL){
/* for each frame read */
VXfupdate(VXout, VXin); /* update global constants */
VXwriteframe(VXout,vxlist); /* write frame */
VXdellist(vxlist); /* delete the frame */
}
}
VXclose(VXin); /* close input file */
VXclose(VXout); /* close output file */
exit(0);
}
Any VisionX program should be able to deal with any VisionX file, and should accept the flexible VisionX command line structure. The following code walk through illustrates the five stage framework that is used in all structured VisionX programs. 1. Global declarationsSpecify the VisionX include file and declare VisionX file structures.The VisXV4.h file is required for every VisionX program Vutil.h is an optional file that contains a number of useful macros and various standard include files such as stdio.h, math.h and string(s).h.
#include "VisXV4.h" /* VisionX structure include file */
#include "Vutil.h" /* useful macros, stdio.h etc. */
/* */
VisXfile_t *VXin, /* input file structure */
*VXout; /* output file structure */
VisXelem_t *vxlist; /* VisX data structure */
In general, every file is associated with a file structure ``VisXfile_t *'', also a data list ``VisXelem_t *'' is used to hold the data read from or to be written to files. 2. Command line parametersDefine the prefixes for the command line parameters.The par structure contains a prefix, a value and a brief description for each command line parameter. Both positional (without prefix) and prefix spefication of command line parameters is supported. By convention "if=" specifies the primary input file and "of=" specifies the primary output file.
VXparam_t par[] = /* command line structure */
{
{ "if=", 0, "input file vcp: file copy"},
{ "of=", 0, "output file"},
{ "-f", 0, "frame-i/o option"},
{ 0, 0, 0}, /* list termination */
};
#define IVAL par[0].val
#define OVAL par[1].val
#define FFLAG par[2].val
Each prefix is specified by two statements. For example, the
string matched to the "of=" command parameter is referred to
by OVAL in the program. The VXparse subroutine parses the command
line and sets the .val elements of the par data structure to
the text strings associated with the matched parameters.
If the user does not specify the "of=" parameter then
OVAL is set to a NULL string by VXparse.
3. Main program initializationParse the command line and open files.The second argument to VXopen specifies if a file is to be opened for reading(0) or writing (1).
main(argc, argv)
int argc;
char *argv[];
{
VXparse(&argc, &argv, par); /* parse the command line */
VXin = VXopen(IVAL, 0); /* open input file */
VXout = VXopen(OVAL, 1); /* open the output file */
4. Main program bodyThere are two modes of processing VisionX files. Either the whole file may be read into a list structure or file "frames" may be read one at a time. The vcp program illustrates both of these modes. For complete file i/o the structure is:
vxlist = VXread(VXin); /* read data */
/* do any modifications to vxlist or create */
/* a separate list for output */
VXwrite(VXout, vxlist); /* write data */
To process the data file one frame at a time the structure is:
while ((vxlist = VXreadframe(VXin)) != VXNIL){
/* for each frame read */
VXfupdate(VXout, VXin); /* update global constants */
/* do any modifications to vxlist or create */
/* a separate list for output */
VXwriteframe(VXout,vxlist); /* write frame */
VXdellist(vxlist); /* delete the frame */
}
In this case a new vxlist is created with each call to VXreadframe.
Any global constants that are to be used for all frames are maintained
in a list VXflist(VXout). The VXupdate command ensures that this
list is maintained with any new global information that is extracted
from the input file with the call to VXreadframe.
5. File closing and exitAny well written program should close all opened files and exit with exit(0).
VXclose(VXin); /* close input file */
VXclose(VXout); /* close output file */
exit(0);
}
A. P. Reeves, © Copyright 1998-2012 11/12/2012 |