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/* pbmreduce.c - read a portable bitmap and reduce it N times
**
** 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 <limits.h>
#include "pbm.h"
#include "mallocvar.h"
int
main( argc, argv )
int argc;
char* argv[];
{
FILE* ifp;
register bit** bitslice;
register bit* newbitrow;
register bit* nbP;
int argn, n, rows, cols, format, newrows, newcols;
int row, col, limitcol, subrow, subcol, count, direction;
const char* const usage = "[-floyd|-fs | -threshold] [-value <val>] N [pbmfile]";
int halftone;
#define QT_FS 1
#define QT_THRESH 2
#define SCALE 1024
#define HALFSCALE 512
long threshval, sum;
long* thiserr; /* used for Floyd-Steinberg stuff */
long* nexterr; /* used for Floyd-Steinberg stuff */
long* temperr;
pbm_init( &argc, argv );
argn = 1;
halftone = QT_FS;
threshval = HALFSCALE;
while ( argn < argc && argv[argn][0] == '-' && argv[argn][1] != '\0' )
{
if ( pm_keymatch( argv[argn], "-fs", 2 ) ||
pm_keymatch( argv[argn], "-floyd", 2 ) )
halftone = QT_FS;
else if ( pm_keymatch( argv[argn], "-threshold", 2 ) )
halftone = QT_THRESH;
else if ( pm_keymatch( argv[argn], "-value", 2 ) )
{
float f;
++argn;
if ( argn == argc || sscanf( argv[argn], "%f", &f ) != 1 ||
f < 0.0 || f > 1.0 )
pm_usage( usage );
threshval = f * SCALE;
}
else
pm_usage( usage );
++argn;
}
if ( argn == argc )
pm_usage( usage );
if ( sscanf( argv[argn], "%d", &n ) != 1 )
pm_usage( usage );
if ( n < 2 )
pm_error( "N must be greater than 1" );
if (n > INT_MAX / n)
pm_error("Scale argument too large. You specified %d", n);
++argn;
if ( argn == argc )
ifp = stdin;
else
{
ifp = pm_openr( argv[argn] );
++argn;
}
if ( argn != argc )
pm_usage( usage );
pbm_readpbminit( ifp, &cols, &rows, &format );
bitslice = pbm_allocarray( cols, n );
newrows = rows / n;
newcols = cols / n;
pbm_writepbminit( stdout, newcols, newrows, 0 );
newbitrow = pbm_allocrow( newcols );
if (halftone == QT_FS) {
unsigned int col;
/* Initialize Floyd-Steinberg. */
MALLOCARRAY(thiserr, newcols + 2);
MALLOCARRAY(nexterr, newcols + 2);
if (thiserr == NULL || nexterr == NULL)
pm_error("out of memory");
srand(pm_randseed());
for (col = 0; col < newcols + 2; ++col)
thiserr[col] = (rand() % SCALE - HALFSCALE) / 4;
/* (random errors in [-SCALE/8 .. SCALE/8]) */
} else {
/* These variables are meaningless in this case, and the values
should never be used.
*/
thiserr = NULL;
nexterr = NULL;
}
direction = 1;
for ( row = 0; row < newrows; ++row )
{
for ( subrow = 0; subrow < n; ++subrow )
pbm_readpbmrow( ifp, bitslice[subrow], cols, format );
if ( halftone == QT_FS )
for ( col = 0; col < newcols + 2; ++col )
nexterr[col] = 0;
if ( direction )
{
col = 0;
limitcol = newcols;
nbP = newbitrow;
}
else
{
col = newcols - 1;
limitcol = -1;
nbP = &(newbitrow[col]);
}
do
{
sum = 0;
count = 0;
for ( subrow = 0; subrow < n; ++subrow )
for ( subcol = 0; subcol < n; ++subcol )
if ( row * n + subrow < rows && col * n + subcol < cols )
{
count += 1;
if ( bitslice[subrow][col * n + subcol] == PBM_WHITE )
sum += 1;
}
sum = ( sum * SCALE ) / count;
if ( halftone == QT_FS )
sum += thiserr[col + 1];
if ( sum >= threshval )
{
*nbP = PBM_WHITE;
if ( halftone == QT_FS )
sum = sum - threshval - HALFSCALE;
}
else
*nbP = PBM_BLACK;
if ( halftone == QT_FS )
{
if ( direction )
{
thiserr[col + 2] += ( sum * 7 ) / 16;
nexterr[col ] += ( sum * 3 ) / 16;
nexterr[col + 1] += ( sum * 5 ) / 16;
nexterr[col + 2] += ( sum ) / 16;
}
else
{
thiserr[col ] += ( sum * 7 ) / 16;
nexterr[col + 2] += ( sum * 3 ) / 16;
nexterr[col + 1] += ( sum * 5 ) / 16;
nexterr[col ] += ( sum ) / 16;
}
}
if ( direction )
{
++col;
++nbP;
}
else
{
--col;
--nbP;
}
}
while ( col != limitcol );
pbm_writepbmrow( stdout, newbitrow, newcols, 0 );
if ( halftone == QT_FS )
{
temperr = thiserr;
thiserr = nexterr;
nexterr = temperr;
direction = ! direction;
}
}
pm_close( ifp );
pm_close( stdout );
exit( 0 );
}
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