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/* pgmenhance.c - edge-enhance a portable graymap
**
** Copyright (C) 1989, 1991 by Jef Poskanzer.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation. This software is provided "as is" without express or
** implied warranty.
*/
#include "pgm.h"
int
main(int argc, char * argv[] ) {
FILE* ifp;
gray* prevrow;
gray* thisrow;
gray* nextrow;
gray* temprow;
gray* newrow;
int argn, n, rows, cols, row, col;
float phi, omphi;
gray maxval;
int format;
const char* const usage = "[-N] [pgmfile] ( 1 <= N <= 9, default = 9 )";
pgm_init( &argc, argv );
argn = 1;
n = 9;
if ( argn < argc && argv[argn][0] == '-' && argv[argn][1] != '\0' ) {
if ( sscanf( &(argv[argn][1]), "%d", &n ) != 1 )
pm_usage( usage );
if ( n < 1 || n > 9 )
pm_usage( usage );
++argn;
}
if ( argn != argc ) {
ifp = pm_openr( argv[argn] );
++argn;
} else
ifp = stdin;
if ( argn != argc )
pm_usage( usage );
pgm_readpgminit( ifp, &cols, &rows, &maxval, &format );
prevrow = pgm_allocrow( cols );
thisrow = pgm_allocrow( cols );
nextrow = pgm_allocrow( cols );
pgm_writepgminit( stdout, cols, rows, maxval, 0 );
newrow = pgm_allocrow( cols );
/* The edge enhancing technique is taken from Philip R. Thompson's "xim"
** program, which in turn took it from section 6 of "Digital Halftones by
** Dot Diffusion", D. E. Knuth, ACM Transaction on Graphics Vol. 6, No. 4,
** October 1987, which in turn got it from two 1976 papers by J. F. Jarvis
** et. al.
*/
phi = n / 10.0;
omphi = 1.0 - phi;
/* First row. */
pgm_readpgmrow( ifp, thisrow, cols, maxval, format );
pgm_writepgmrow( stdout, thisrow, cols, maxval, 0 );
pgm_readpgmrow( ifp, nextrow, cols, maxval, format );
/* Other rows. */
for ( row = 1; row < rows - 1; row++ ) {
temprow = prevrow;
prevrow = thisrow;
thisrow = nextrow;
nextrow = temprow;
pgm_readpgmrow( ifp, nextrow, cols, maxval, format );
newrow[0] = thisrow[0];
for (col = 1; col < cols - 1; col++) {
/* Compute the sum of the neighborhood. */
long sum, newval;
sum =
(long) prevrow[col-1] + (long) prevrow[col] +
(long) prevrow[col+1] +
(long) thisrow[col-1] + (long) thisrow[col] +
(long) thisrow[col+1] +
(long) nextrow[col-1] + (long) nextrow[col] +
(long) nextrow[col+1];
/* Now figure new value. */
newval = ( ( thisrow[col] - phi * sum / 9 ) / omphi + 0.5 );
if ( newval < 0 )
newrow[col] = 0;
else if ( newval > maxval )
newrow[col] = maxval;
else
newrow[col] = newval;
}
newrow[cols - 1] = thisrow[cols - 1];
pgm_writepgmrow( stdout, newrow, cols, maxval, 0 );
}
pm_close( ifp );
/* Last row. */
pgm_writepgmrow( stdout, nextrow, cols, maxval, 0 );
pm_close( stdout );
exit( 0 );
}
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