/* detect zero-crossings
 *
 * 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
 * 11/11/10
 * 	- small cleanups
 * 	- gtkdoc
 */

/*

	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., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  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 <glib/gi18n-lib.h>

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

#include <vips/vips.h>
#include <vips/vips7compat.h>

#define LOOP(TYPE) \
	{ \
		for (i = 0; i < ne; i++) { \
			TYPE p1 = ((TYPE *) p)[i]; \
			TYPE p2 = ((TYPE *) p)[i + ba]; \
\
			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 *out_region, void *seq, void *a, void *b)
{
	REGION *ir = (REGION *) seq;
	IMAGE *in = (IMAGE *) a;
	int flag = GPOINTER_TO_INT(b);
	Rect irect;
	Rect *r = &out_region->valid;

	/* Range of pixels we loop over.
	 */
	int le = r->left;
	int to = r->top;
	int bo = IM_RECT_BOTTOM(r);
	int ba = in->Bands;
	int ne = ba * 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++) {
		VipsPel *p = IM_REGION_ADDR(ir, le, y);
		VipsPel *q = IM_REGION_ADDR(out_region, 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:
			g_assert(0);
		}
	}

	return 0;
}

/**
 * im_zerox:
 * @in: input image
 * @out: output image
 * @sign: detect positive or negative zero crossings
 *
 * im_zerox() detects the positive or negative zero crossings @in,
 * depending on @sign. If @sign is -1, negative zero crossings are returned,
 * if @sign is 1, positive zero crossings are returned.
 *
 * The output image is byte with zero crossing set to 255 and all other values
 * set to zero. Input can have any number of channels, and be any non-complex
 * type.
 *
 * See also: im_conv(), im_rot90.
 *
 * Returns: 0 on success, -1 on error
 */
int
im_zerox(IMAGE *in, IMAGE *out, int sign)
{
	IMAGE *t1;

	if (sign != -1 && sign != 1) {
		im_error("im_zerox", "%s", _("flag not -1 or 1"));
		return -1;
	}
	if (in->Xsize < 2) {
		im_error("im_zerox", "%s", _("image too narrow"));
		return -1;
	}
	if (!(t1 = im_open_local(out, "im_zerox", "p")) ||
		im_piocheck(in, t1) ||
		im_check_uncoded("im_zerox", in) ||
		im_check_noncomplex("im_zerox", in))
		return -1;
	if (vips_bandfmt_isuint(in->BandFmt))
		/* 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->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(sign)))
		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;
}
