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/* pgmedge.c - edge-detect a portable graymap
**
** Copyright (C) 1989 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 <math.h>
#include "pgm.h"
int
main( argc, argv )
int argc;
char *argv[];
{
FILE *ifp;
gray *row0, *row1, *row2, *tmprow, *orow;
int argn, rows, cols, format, row;
register int col;
gray maxval;
double sum1, sum2, sum;
char *usage = "[pgmfile]";
pgm_init( &argc, argv );
argn = 1;
if ( argn != argc )
{
ifp = pm_openr( argv[argn] );
argn++;
}
else
ifp = stdin;
if ( argn != argc )
pm_usage( usage );
pgm_pbmmaxval = 255; /* use larger value for better results */
pgm_readpgminit( ifp, &cols, &rows, &maxval, &format );
if ( cols < 3 || rows < 3 )
pm_error( "the image is too small" );
row0 = pgm_allocrow( cols );
row1 = pgm_allocrow( cols );
row2 = pgm_allocrow( cols );
orow = pgm_allocrow( cols );
pgm_writepgminit( stdout, cols, rows, maxval, 0 );
/* Read in the first two rows. */
pgm_readpgmrow( ifp, row0, cols, maxval, format );
pgm_readpgmrow( ifp, row1, cols, maxval, format );
/* Write out the first row, all zeros. */
for ( col = 0; col < cols; ++col )
orow[col] = 0;
pgm_writepgmrow( stdout, orow, cols, maxval, 0 );
/* Now the rest of the image -- read in the next row, and write
** write out the current row.
*/
for ( row = 1; row < rows - 1; row++ )
{
pgm_readpgmrow( ifp, row2, cols, maxval, format );
for ( col = 1; col < cols - 1; col++ )
{
sum1 = (double) row0[col+1] - (double) row0[col-1] +
2.0 * ( (double) row1[col+1] - (double) row1[col-1] ) +
(double) row2[col+1] - (double) row2[col-1];
sum2 = ( (double) row2[col-1] + 2.0 * (double) row2[col] +
(double) row2[col+1] ) -
( (double) row0[col-1] + 2.0 * (double) row0[col] +
(double) row0[col+1] );
sum = sqrt( sum1 * sum1 + sum2 * sum2 );
sum /= 1.8; /* arbitrary scaling factor */
if ( sum > maxval ) sum = maxval;
orow[col] = sum;
}
/* Write out a row. */
pgm_writepgmrow( stdout, orow, cols, maxval, 0 );
/* Rotate rows. */
tmprow = row0;
row0 = row1;
row1 = row2;
row2 = tmprow;
}
pm_close( ifp );
/* And write the last row, zeros again. */
for ( col = 0; col < cols; ++col )
orow[col] = 0;
pgm_writepgmrow( stdout, orow, cols, maxval, 0 );
pm_close( stdout );
exit( 0 );
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.