/* @(#)  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 );
}