/* identity LUTs
 *
 * Copyright 1991, N. Dessipris.
 *
 * Author N. Dessipris
 * Written on 11/03/1991
 * Updated on:
 * 18/6/93 JC
 *	- im_outcheck() call added
 *	- ANSIfied
 * 24/8/94 JC
 *	- im_identity_ushort() added
 * 24/3/10
 * 	- gtkdoc
 * 3/7/13
 * 	- redo as a class
 */

/*

	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 <math.h>

#include <vips/vips.h>

#include "pcreate.h"

typedef struct _VipsIdentity {
	VipsCreate parent_instance;

	int bands;
	gboolean ushort;
	int size;

} VipsIdentity;

typedef VipsCreateClass VipsIdentityClass;

G_DEFINE_TYPE(VipsIdentity, vips_identity, VIPS_TYPE_CREATE);

#define IDENTITY(TYPE) \
	{ \
		TYPE *q = (TYPE *) VIPS_REGION_ADDR(out_region, le, 0); \
\
		for (x = le; x < ri; x++) { \
			for (i = 0; i < identity->bands; i++) \
				q[i] = x; \
\
			q += identity->bands; \
		} \
	}

static int
vips_identity_gen(VipsRegion *out_region,
	void *seq, void *a, void *b, gboolean *stop)
{
	VipsIdentity *identity = (VipsIdentity *) a;
	VipsRect *r = &out_region->valid;
	int le = r->left;
	int ri = VIPS_RECT_RIGHT(r);

	int x, i;

	if (identity->ushort) {
		IDENTITY(unsigned short);
	}
	else {
		IDENTITY(unsigned char);
	}

	return 0;
}

static int
vips_identity_build(VipsObject *object)
{
	VipsCreate *create = VIPS_CREATE(object);
	VipsIdentity *identity = (VipsIdentity *) object;

	if (VIPS_OBJECT_CLASS(vips_identity_parent_class)->build(object))
		return -1;

	vips_image_init_fields(create->out,
		identity->ushort ? identity->size : 256, 1, identity->bands,
		identity->ushort ? VIPS_FORMAT_USHORT : VIPS_FORMAT_UCHAR,
		VIPS_CODING_NONE, VIPS_INTERPRETATION_HISTOGRAM,
		1.0, 1.0);

	if (vips_image_pipelinev(create->out, VIPS_DEMAND_STYLE_ANY, NULL) ||
		vips_image_generate(create->out,
			NULL, vips_identity_gen, NULL, identity, NULL))
		return -1;

	return 0;
}

static void
vips_identity_class_init(VipsIdentityClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "identity";
	vobject_class->description =
		_("make a 1D image where pixel values are indexes");
	vobject_class->build = vips_identity_build;

	VIPS_ARG_INT(class, "bands", 3,
		_("Bands"),
		_("Number of bands in LUT"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsIdentity, bands),
		1, 100000, 1);

	VIPS_ARG_BOOL(class, "ushort", 4,
		_("Ushort"),
		_("Create a 16-bit LUT"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsIdentity, ushort),
		FALSE);

	VIPS_ARG_INT(class, "size", 5,
		_("Size"),
		_("Size of 16-bit LUT"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsIdentity, size),
		1, 65536, 65536);
}

static void
vips_identity_init(VipsIdentity *identity)
{
	identity->bands = 1;
	identity->ushort = FALSE;
	identity->size = 65536;
}

/**
 * vips_identity:
 * @out: (out): output image
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @bands: number of bands to create
 * * @ushort: %TRUE for an unsigned short identity
 * * @size: number of LUT elements for a ushort image
 *
 * Creates an identity lookup table, ie. one which will leave an image
 * unchanged when applied with vips_maplut(). Each entry in the table has a
 * value equal to its position.
 *
 * Use the arithmetic operations on these tables to make LUTs representing
 * arbitrary functions.
 *
 * Normally LUTs are 8-bit. Set @ushort to create a 16-bit table.
 *
 * Normally 16-bit tables have 65536 entries. You can set this smaller with
 * @size.
 *
 * See also: vips_xyz(), vips_maplut().
 *
 * Returns: 0 on success, -1 on error
 */
int
vips_identity(VipsImage **out, ...)
{
	va_list ap;
	int result;

	va_start(ap, out);
	result = vips_call_split("identity", ap, out);
	va_end(ap);

	return result;
}
