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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( argc, argv )
- int argc;
- char* argv[];
- {
- FILE* ifp;
- gray* prevrow;
- gray* thisrow;
- gray* nextrow;
- gray* temprow;
- gray* newrow;
- register gray* ngP;
- int argn, n, rows, cols, row, col;
- float phi, omphi;
- gray maxval;
- long sum, newval;
- int format;
- char* 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_pbmmaxval = 255; /* use a larger value for better (?) results */
- 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 );
-
- ngP = newrow;
- *ngP = thisrow[0];
- ngP++;
- for ( col = 1; col < cols - 1; col++, ngP++ )
- {
- /* Compute the sum of the neighborhood. */
- 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 )
- *ngP = 0;
- else if ( newval > maxval )
- *ngP = maxval;
- else
- *ngP = newval;
- }
- *ngP = 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 );
- }
-