/* Subtract two images
 *
 * Copyright: 1990, N. Dessipris.
 *
 * Author: Nicos Dessipris
 * Written on: 02/05/1990
 * Modified on: 
 * 29/4/93 J.Cupitt
 *	- now works for partial images
 * 1/7/93 JC
 * 	- adapted for partial v2
 * 9/5/95 JC
 *	- simplified: now just handles 10 cases (instead of 50), using
 *	  im_clip2*() to help
 *	- now uses im_wrapmany() rather than im_generate()
 * 12/6/95 JC
 * 	- new im_add() adapted to make this
 * 31/5/96 JC
 *	- what was this SWAP() stuff? failed for small - big!
 * 22/8/03 JC
 *	- cast up more quickly to help accuracy
 * 27/9/04
 *	- updated for 1 band $op n band image -> n band image case
 * 8/12/06
 * 	- add liboil support
 * 18/8/08
 * 	- revise upcasting system
 * 	- add gtkdoc comments
 * 	- remove separate complex case, just double size
 * 31/7/10
 * 	- remove liboil
 * 23/8/11
 * 	- rewrite as a class from add.c
 */

/*

    Copyright (C) 1991-2005 The National Gallery

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU 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 General Public License for more details.

    You should have received a copy of the GNU 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

 */

/*
#define DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include <vips/vips.h>

#include "binary.h"

/**
 * VipsSubtract:
 * @in1: input image 
 * @in2: input image 
 * @out: output image
 *
 * This operation calculates @in1 - @in2 and writes the result to @out. 
 *
 * If the images differ in size, the smaller image is enlarged to match the
 * larger by adding zero pixels along the bottom and right.
 *
 * If the number of bands differs, one of the images 
 * must have one band. In this case, an n-band image is formed from the 
 * one-band image by joining n copies of the one-band image together, and then
 * the two n-band images are operated upon.
 *
 * The two input images are cast up to the smallest common type (see table 
 * Smallest common format in 
 * <link linkend="VIPS-arithmetic">arithmetic</link>), then the 
 * following table is used to determine the output type:
 *
 * <table>
 *   <title>VipsSubtract type promotion</title>
 *   <tgroup cols='2' align='left' colsep='1' rowsep='1'>
 *     <thead>
 *       <row>
 *         <entry>input type</entry>
 *         <entry>output type</entry>
 *       </row>
 *     </thead>
 *     <tbody>
 *       <row>
 *         <entry>uchar</entry>
 *         <entry>short</entry>
 *       </row>
 *       <row>
 *         <entry>char</entry>
 *         <entry>short</entry>
 *       </row>
 *       <row>
 *         <entry>ushort</entry>
 *         <entry>int</entry>
 *       </row>
 *       <row>
 *         <entry>short</entry>
 *         <entry>int</entry>
 *       </row>
 *       <row>
 *         <entry>uint</entry>
 *         <entry>int</entry>
 *       </row>
 *       <row>
 *         <entry>int</entry>
 *         <entry>int</entry>
 *       </row>
 *       <row>
 *         <entry>float</entry>
 *         <entry>float</entry>
 *       </row>
 *       <row>
 *         <entry>double</entry>
 *         <entry>double</entry>
 *       </row>
 *       <row>
 *         <entry>complex</entry>
 *         <entry>complex</entry>
 *       </row>
 *       <row>
 *         <entry>double complex</entry>
 *         <entry>double complex</entry>
 *       </row>
 *     </tbody>
 *   </tgroup>
 * </table>
 *
 * In other words, the output type is just large enough to hold the whole
 * range of possible values.
 *
 * See also: #VipsAdd, #VipsLinear.
 *
 * Returns: 0 on success, -1 on error
 */

typedef VipsBinary VipsSubtract;
typedef VipsBinaryClass VipsSubtractClass;

G_DEFINE_TYPE( VipsSubtract, vips_subtract, VIPS_TYPE_BINARY );

#define LOOP( IN, OUT ) { \
	IN *left = (IN *) in[0]; \
	IN *right = (IN *) in[1]; \
	OUT *q = (OUT *) out; \
	\
	for( x = 0; x < sz; x++ ) \
		q[x] = left[x] - right[x]; \
}

static void
vips_subtract_buffer( VipsArithmetic *arithmetic, 
	PEL *out, PEL **in, int width )
{
	VipsImage *im = arithmetic->ready[0];

	/* Complex just doubles the size.
	 */
	const int sz = width * vips_image_get_bands( im ) * 
		(vips_band_format_iscomplex( vips_image_get_format( im ) ) ? 
		 	2 : 1);

	int x;

	/* Keep types here in sync with bandfmt_subtract[] 
	 * below.
         */
        switch( vips_image_get_format( im ) ) {
        case VIPS_FORMAT_CHAR: 	LOOP( signed char, signed short ); break; 
        case VIPS_FORMAT_UCHAR:	LOOP( unsigned char, signed short ); break; 
        case VIPS_FORMAT_SHORT:	LOOP( signed short, signed int ); break; 
        case VIPS_FORMAT_USHORT:LOOP( unsigned short, signed int ); break; 
        case VIPS_FORMAT_INT: 	LOOP( signed int, signed int ); break; 
        case VIPS_FORMAT_UINT: 	LOOP( unsigned int, signed int ); break; 

        case VIPS_FORMAT_FLOAT: 		
        case VIPS_FORMAT_COMPLEX:
		LOOP( float, float ); 
		break; 

        case VIPS_FORMAT_DOUBLE:	
        case VIPS_FORMAT_DPCOMPLEX:
		LOOP( double, double ); 
		break;

        default:
		g_assert( 0 );
        }
}

/* Save a bit of typing.
 */
#define UC VIPS_FORMAT_UCHAR
#define C VIPS_FORMAT_CHAR
#define US VIPS_FORMAT_USHORT
#define S VIPS_FORMAT_SHORT
#define UI VIPS_FORMAT_UINT
#define I VIPS_FORMAT_INT
#define F VIPS_FORMAT_FLOAT
#define X VIPS_FORMAT_COMPLEX
#define D VIPS_FORMAT_DOUBLE
#define DX VIPS_FORMAT_DPCOMPLEX

/* Type promotion for subtraction. Sign and value preserving. Make sure these
 * match the case statement in vips_subtract_buffer() above.
 */
static const VipsBandFormat bandfmt_subtract[10] = {
/* UC  C   US  S   UI  I  F  X  D  DX */
   S,  S,  I,  I,  I,  I, F, X, D, DX
};

static void
vips_subtract_class_init( VipsSubtractClass *class )
{
	VipsObjectClass *object_class = (VipsObjectClass *) class;
	VipsArithmeticClass *aclass = VIPS_ARITHMETIC_CLASS( class );

	object_class->nickname = "subtract";
	object_class->description = _( "subtract two images" );

	vips_arithmetic_set_format_table( aclass, bandfmt_subtract );

	aclass->process_line = vips_subtract_buffer;
}

static void
vips_subtract_init( VipsSubtract *subtract )
{
}

int
vips_subtract( VipsImage *left, VipsImage *right, VipsImage **out, ... )
{
	va_list ap;
	int result;

	va_start( ap, out );
	result = vips_call_split( "subtract", ap, left, right, out );
	va_end( ap );

	return( result );
}