/* Build a LUT from a set of x/y points.
 *
 * Written on: 26/9/06
 * 	- from im_invertlut()
 * 9/10/06
 * 	- don't output x values
 * 18/3/09
 * 	- saner limit and rounding behaviour
 * 30/3/09
 * 	- argh, fixed again
 * 22/6/09
 *	- more fixes for tables that don't start at zero (thanks Jack)
 * 23/3/10
 * 	- gtkdoc
 * 2/7/13
 * 	- convert to a class
 * 10/12/13
 * 	- be more forgiving about x vales not quite integers
 */

/*

	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

 */

/*
#define DEBUG
 */

#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 _VipsBuildlut {
	VipsCreate parent_instance;

	/* Input image.
	 */
	VipsImage *in;

	/* .. and cast to a matrix.
	 */
	VipsImage *mat;

	int xlow;	   /* Index 0 in output is this x */
	int lut_size;  /* Number of output elements to generate */
	double **data; /* Matrix row pointers */
	double *buf;   /* Output buffer */
} VipsBuildlut;

typedef VipsCreateClass VipsBuildlutClass;

G_DEFINE_TYPE(VipsBuildlut, vips_buildlut, VIPS_TYPE_CREATE);

static void
vips_buildlut_dispose(GObject *gobject)
{
	VipsBuildlut *lut = (VipsBuildlut *) gobject;

	VIPS_FREE(lut->data);
	VIPS_FREE(lut->buf);
	VIPS_UNREF(lut->mat);

	G_OBJECT_CLASS(vips_buildlut_parent_class)->dispose(gobject);
}

/* Use this to sort our input rows by the first column.
 */
static int
vips_buildlut_compare(const void *a, const void *b)
{
	double **r1 = (double **) a;
	double **r2 = (double **) b;

	double diff = r1[0][0] - r2[0][0];

	if (diff > 0)
		return 1;
	else if (diff == 0)
		return 0;
	else
		return -1;
}

static int
vips_buildlut_build_init(VipsBuildlut *lut)
{
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS(lut);

	int y;
	int xlow, xhigh;

	/* Need xlow and xhigh to get the size of the LUT we build.
	 */
	xlow = xhigh = *VIPS_MATRIX(lut->mat, 0, 0);
	for (y = 0; y < lut->mat->Ysize; y++) {
		double v = *VIPS_MATRIX(lut->mat, 0, y);

		/* Allow for being a bit off.
		 */
		if (VIPS_FABS(v - VIPS_RINT(v)) > 0.001) {
			vips_error(class->nickname,
				_("x value row %d not an int"), y);
			return -1;
		}

		v = VIPS_RINT(v);

		if (v < xlow)
			xlow = v;
		if (v > xhigh)
			xhigh = v;
	}
	lut->xlow = xlow;
	lut->lut_size = xhigh - xlow + 1;

	if (lut->lut_size < 1) {
		vips_error(class->nickname, "%s", _("x range too small"));
		return -1;
	}

	if (!(lut->data = VIPS_ARRAY(NULL, lut->mat->Ysize, double *)))
		return -1;
	for (y = 0; y < lut->mat->Ysize; y++)
		lut->data[y] = VIPS_MATRIX(lut->mat, 0, y);

	if (!(lut->buf = VIPS_ARRAY(NULL,
			  lut->lut_size * (lut->mat->Xsize - 1), double)))
		return -1;

	/* Sort by 1st column in input.
	 */
	qsort(lut->data, lut->mat->Ysize,
		sizeof(double *), vips_buildlut_compare);

#ifdef DEBUG
	printf("Input table, sorted by 1st column\n");
	for (y = 0; y < lut->mat->Ysize; y++) {
		int x;

		printf("%.4d ", y);

		for (x = 0; x < lut->mat->Xsize; x++)
			printf("%.9f ", lut->data[y][x]);

		printf("\n");
	}
#endif /*DEBUG*/

	return 0;
}

static int
vips_buildlut_build_create(VipsBuildlut *lut)
{
	const int xlow = lut->xlow;
	const VipsImage *mat = lut->mat;
	const int xsize = mat->Xsize;
	const int ysize = mat->Ysize;
	const int bands = xsize - 1;
	const int xlast = lut->data[ysize - 1][0];

	int b, i, x;

	/* Do each output channel separately.
	 */
	for (b = 0; b < bands; b++) {
		for (i = 0; i < ysize - 1; i++) {
			const int x1 = VIPS_RINT(lut->data[i][0]);
			const int x2 = VIPS_RINT(lut->data[i + 1][0]);
			const int dx = x2 - x1;
			const double y1 = lut->data[i][b + 1];
			const double y2 = lut->data[i + 1][b + 1];
			const double dy = y2 - y1;

			for (x = 0; x < dx; x++)
				lut->buf[b + (x + x1 - xlow) * bands] =
					y1 + x * dy / dx;
		}

		/* We are inclusive: pop the final value in by hand.
		 */
		lut->buf[b + (xlast - xlow) * bands] =
			lut->data[ysize - 1][b + 1];
	}

	return 0;
}

static int
vips_buildlut_build(VipsObject *object)
{
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS(object);
	VipsCreate *create = VIPS_CREATE(object);
	VipsBuildlut *lut = (VipsBuildlut *) object;

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

	if (vips_check_matrix(class->nickname, lut->in, &lut->mat))
		return -1;

	if (vips_buildlut_build_init(lut) ||
		vips_buildlut_build_create(lut))
		return -1;

	vips_image_init_fields(create->out,
		lut->lut_size, 1, lut->mat->Xsize - 1,
		VIPS_FORMAT_DOUBLE, VIPS_CODING_NONE,
		VIPS_INTERPRETATION_HISTOGRAM, 1.0, 1.0);
	if (vips_image_write_line(create->out, 0, (VipsPel *) lut->buf))
		return -1;

	return 0;
}

static void
vips_buildlut_class_init(VipsBuildlutClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);

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

	vobject_class->nickname = "buildlut";
	vobject_class->description = _("build a look-up table");
	vobject_class->build = vips_buildlut_build;

	VIPS_ARG_IMAGE(class, "in", 0,
		_("Input"),
		_("Matrix of XY coordinates"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsBuildlut, in));
}

static void
vips_buildlut_init(VipsBuildlut *lut)
{
}

/**
 * vips_buildlut: (method)
 * @in: input matrix
 * @out: (out): output image
 * @...: %NULL-terminated list of optional named arguments
 *
 * This operation builds a lookup table from a set of points. Intermediate
 * values are generated by piecewise linear interpolation. The lookup table is
 * always of type #VIPS_FORMAT_DOUBLE, use vips_cast() to change it to the
 * type you need.
 *
 * For example, consider this 2 x 2 matrix of (x, y) coordinates:
 *
 * |[
 *     |-------|-------|
 *     | 0     | 0     |
 *     |-------|-------|
 *     | 255   | 100   |
 *     |-------|-------|
 * ]|
 *
 * We then generate a 1 x 256 element LUT like this:
 *
 * |[
 *     |-------|-------|
 *     | Index | Value |
 *     |-------|-------|
 *     | 0     | 0     |
 *     |-------|-------|
 *     | 1     | 0.4   |
 *     |-------|-------|
 *     | etc.  | 0.4   |
 *     |-------|-------|
 *     | 255   | 100   |
 *     |-------|-------|
 * ]|
 *
 * This is then written as the output image, with the left column giving the
 * index in the image to place the value.
 *
 * The (x, y) points don't need to be sorted: we do that. You can have
 * several Ys, each becomes a band in the output LUT. You don't need to
 * start at zero, any integer will do, including negatives.
 *
 * See also: vips_identity(), vips_invertlut(), vips_cast(), vips_maplut().
 *
 * Returns: 0 on success, -1 on error
 */
int
vips_buildlut(VipsImage *in, VipsImage **out, ...)
{
	va_list ap;
	int result;

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

	return result;
}
