libvips/libsrc/convolution/im_zerox.c

/* @(#) Functions which detects the +ve and -ve edges of
 * @(#) zero crossings of an image depending on the flag 
 * @(#) Function im_zerox() assumes that the imin file is an integer image
 * @(#) either memory mapped or in a buffer.
 * @(#)  The output image is byte with 
 * @(#)  zero crossing set to 255 and all othre values set to zero
 * @(#)
 * @(#) int im_zerox(pimin, pimout, flag)
 * @(#) IMAGE *pimin, *pimout;
 * @(#) int flag;
 * @(#)
 * @(#) All functions return 0 on success and -1 on error
 * @(#)
 *
 * Copyright: 1990, N. Dessipris.
 *
 * Author: Nicos Dessipris
 * Written on: 12/02/1990
 * Modified on : 
 * 1/2/95 JC
 *	- rewritten for PIO
 *	- some bugs removed
 * 11/5/06
 * 	- small clean ups
 */

/*

    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 <stdlib.h>

#include <vips/vips.h>

#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/

#define loop( TYPE ) \
	for( i = 0; i < ne; i++ ) { \
		TYPE p1 = ((TYPE *)p)[i]; \
		TYPE p2 = ((TYPE *)p)[i + b]; \
		\
		if( flag == 1 && p1 > 0 && p2 <= 0 ) \
			q[i] = 255; \
		else if( flag == -1 && p1 < 0 && p2 >= 0 ) \
			q[i] = 255; \
		else \
			q[i] = 0; \
	}

/* Zerox generate function.
 */
static int
zerox_gen( REGION *or, REGION *ir, IMAGE *in, int flag )
{
	Rect irect;
	Rect *r = &or->valid;

	/* Range of pixels we loop over. 
	 */
	int le = r->left;
	int to = r->top;
	int bo = IM_RECT_BOTTOM( r );
	int b = in->Bands;
	int ne = b * r->width;

	int i, y;

	/* We need to be able to see one pixel to the right. 
	 */
	irect.top = r->top;
	irect.left = r->left;
	irect.width = r->width + 1;
	irect.height = r->height;
	if( im_prepare( ir, &irect ) )
		return( -1 );
	
	for( y = to; y < bo; y++ ) {
		PEL *p = (PEL *) IM_REGION_ADDR( ir, le, y );
		PEL *q = (PEL *) IM_REGION_ADDR( or, le, y );

		switch( in->BandFmt ) {
		case IM_BANDFMT_CHAR:           loop( signed char ); break;
		case IM_BANDFMT_SHORT:          loop( signed short ); break;
		case IM_BANDFMT_INT:            loop( signed int ); break;
		case IM_BANDFMT_FLOAT:          loop( float ); break;
		case IM_BANDFMT_DOUBLE:         loop( double ); break;

		default:
			error_exit( "im_zerox: internal error" );
			/*NOTREACHED*/
		}
	}

	return( 0 );
} 

int 
im_zerox( IMAGE *in, IMAGE *out, int flag )
{
	IMAGE *t1 = im_open_local( out, "im_zerox#1" , "p" );

	if( !t1 )
		return( -1 );
	if( flag != -1 && flag != 1 ) {
		im_error( "im_zerox", _( "flag not -1 ot 1" ) );
		return( -1 );
	}
        if( im_piocheck( in, t1 ) )
		return( -1 );
	if( im_iscomplex( in ) || in->Coding != IM_CODING_NONE ) {
		im_error( "im_zerox", _( "non-complex uncoded only" ) );
		return( -1 );
	}
	if( in->Xsize < 2 ) {
		im_error( "im_zerox", _( "image too narrow" ) );
		return( -1 );
	}
	if( im_isuint( in ) )
		/* Unsigned type, therefore there will be no zero-crossings.
		 */
		return( im_black( out, in->Xsize, in->Ysize, in->Bands ) );

	/* Force output to be BYTE. Output is narrower than input by 1 pixel.
	 */
	if( im_cp_desc( t1, in ) )
		return( -1 );
	t1->Bbits = IM_BBITS_BYTE;
	t1->BandFmt = IM_BANDFMT_UCHAR;
	t1->Xsize -= 1;

	/* Set hints - THINSTRIP is ok with us.
	 */
	if( im_demand_hint( t1, IM_THINSTRIP, NULL ) )
		return( -1 );

	/* Generate image.
	 */
	if( im_generate( t1, im_start_one, zerox_gen, im_stop_one, 
		in, GINT_TO_POINTER( flag ) ) )
		return( -1 );

	/* Now embed it in a larger image.
	 */
	if( im_embed( t1, out, 0, 0, 0, in->Xsize, in->Ysize ) )
		return( -1 );

	return( 0 );
}