libvips/libsrc/morphology/im_cntlines.c

132 lines
3.0 KiB
C

/* @(#) Function which calculates the number of transitions
* @(#) between black and white for the horizontal or the vertical
* @(#) direction of an image. black<128 , white>=128
* @(#) The function calculates the number of transitions for all
* @(#) Xsize or Ysize and returns the mean of the result
* @(#) Input should be binary one channel
* @(#)
* @(#) int im_cntlines(im, nolines, flag)
* @(#) IMAGE *im;
* @(#) float *nolines;
* @(#) int flag; 0 to cnt horizontal and 1 to count vertical lines
* @(#)
* @(#) Returns 0 on success and -1 on error
*
* Copyright: 1990, N. Dessipris.
*
* Author: Nicos Dessipris
* Written on: 02/05/1990
* Modified on :
*
* 19/9/95 JC
* - tidied up
*/
/*
This file is part of VIPS.
VIPS is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>
#include <stdio.h>
#include <vips/vips.h>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
int
im_cntlines( IMAGE *im, double *nolines, int flag )
{
int x, y;
PEL *line;
int cnt;
/* Is im valid?
*/
if( im_incheck( im ) )
return( -1 );
if( im->Coding != IM_CODING_NONE || im->BandFmt != IM_BANDFMT_UCHAR ||
im->Bands != 1 ) {
im_errormsg( "im_cntlines: 1-band uchar uncoded only" );
return( -1 );
}
if( flag != 0 && flag != 1 ) {
im_errormsg( "im_cntlines: flag should be 0 (horizontal) "
"or 1 (vertical)" );
return( -1 );
}
line = (PEL *) im->data;
if( flag == 1 ) {
/* Count vertical lines.
*/
for( cnt = 0, y = 0; y < im->Ysize; y++ ) {
PEL *p = line;
for( x = 0; x < im->Xsize - 1; x++ ) {
if( p[0] < (PEL)128 && p[1] >= (PEL)128 )
cnt++;
else if( p[0] >= (PEL)128 && p[1] < (PEL)128 )
cnt++;
p++;
}
line += im->Xsize;
}
*nolines = (float) cnt / (2.0 * im->Ysize);
}
else {
/* Count horizontal lines.
*/
for( cnt = 0, y = 0; y < im->Ysize - 1; y++ ) {
PEL *p1 = line;
PEL *p2 = line + im->Xsize;
for( x = 0; x < im->Xsize; x++ ) {
if( *p1 < (PEL)128 && *p2 >= (PEL)128 )
cnt++;
else if( *p1 >= (PEL)128 && *p2 < (PEL)128 )
cnt++;
p1++;
p2++;
}
line += im->Xsize;
}
*nolines = (float)cnt / (2.0 * im->Xsize);
}
return( 0 );
}