/* Perlin noise generator.
 *
 * 24/7/16
 */

/*

	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 VIPS_DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

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

#include <vips/vips.h>

#include "pcreate.h"

typedef struct _VipsPerlin {
	VipsCreate parent_instance;

	int width;
	int height;
	int cell_size;
	gboolean uchar;

	int cells_across;
	int cells_down;

	/* Use this to seed this call of our rng.
	 */
	guint32 seed;
} VipsPerlin;

typedef struct _VipsPerlinClass {
	VipsCreateClass parent_class;

} VipsPerlinClass;

G_DEFINE_TYPE(VipsPerlin, vips_perlin, VIPS_TYPE_CREATE);

/* cos and sin from an angle in 0 - 255.
 */
float vips_perlin_cos[256];
float vips_perlin_sin[256];

typedef struct _Sequence {
	VipsPerlin *perlin;

	/* The position of the last cell we were in. Use this to avoid
	 * regenerating vectors on every pixel lookup.
	 */
	int cell_x;
	int cell_y;

	/* The 2 x 2 grid of unit vectors, with cell_x/cell_y as the top left.
	 */
	float gx[4];
	float gy[4];

} Sequence;

/* Generate a 3 x 3 grid of cells around a point.
 */
static void
vips_perlin_create_cells(VipsPerlin *perlin,
	float gx[4], float gy[4], int cell_x, int cell_y)
{
	int x, y;

	for (y = 0; y < 2; y++)
		for (x = 0; x < 2; x++) {
			int ci = x + y * 2;

			guint32 seed;
			int cx;
			int cy;
			int angle;

			seed = perlin->seed;

			cx = cell_x + x;
			cy = cell_y + y;

			/* When we calculate the seed for this cell, we wrap
			 * around so that our output will tessellate.
			 */

			if (cy >= perlin->cells_down)
				cy = 0;
			seed = vips__random_add(seed, cy);

			if (cx >= perlin->cells_across)
				cx = 0;
			seed = vips__random_add(seed, cx);

			angle = (seed ^ (seed >> 8) ^ (seed >> 16)) & 0xff;

			gx[ci] = vips_perlin_cos[angle];
			gy[ci] = vips_perlin_sin[angle];
		}
}

static int
vips_perlin_stop(void *vseq, void *a, void *b)
{
	Sequence *seq = (Sequence *) vseq;

	VIPS_FREE(seq);

	return 0;
}

static void *
vips_perlin_start(VipsImage *out, void *a, void *b)
{
	VipsPerlin *perlin = (VipsPerlin *) b;

	Sequence *seq;

	if (!(seq = VIPS_NEW(NULL, Sequence)))
		return NULL;

	seq->perlin = perlin;
	seq->cell_x = -1;
	seq->cell_y = -1;

	return seq;
}

/* Smooth linear interpolation, 0 <= x <= 1.
 *
 * https://en.wikipedia.org/wiki/Smoothstep
 */
static float
smootherstep(float x)
{
	return x * x * x * (x * (x * 6 - 15) + 10);
}

static int
vips_perlin_gen(VipsRegion *out_region,
	void *vseq, void *a, void *b, gboolean *stop)
{
	VipsPerlin *perlin = (VipsPerlin *) a;
	VipsRect *r = &out_region->valid;
	Sequence *seq = (Sequence *) vseq;

	int x, y;

	for (y = 0; y < r->height; y++) {
		float *fq = (float *)
			VIPS_REGION_ADDR(out_region, r->left, r->top + y);
		VipsPel *q = (VipsPel *) fq;

		for (x = 0; x < r->width; x++) {
			int cs = perlin->cell_size;
			int cell_x = (r->left + x) / cs;
			int cell_y = (r->top + y) / cs;
			float dx = (x + r->left - cell_x * cs) / (float) cs;
			float dy = (y + r->top - cell_y * cs) / (float) cs;
			float sx = smootherstep(dx);
			float sy = smootherstep(dy);

			float n0, n1;
			float ix0, ix1;
			float p;

			if (cell_x != seq->cell_x ||
				cell_y != seq->cell_y) {
				vips_perlin_create_cells(perlin,
					seq->gx, seq->gy, cell_x, cell_y);
				seq->cell_x = cell_x;
				seq->cell_y = cell_y;
			}

			n0 = -dx * seq->gx[0] + -dy * seq->gy[0];
			n1 = (1 - dx) * seq->gx[1] + -dy * seq->gy[1];
			ix0 = n0 + sx * (n1 - n0);

			n0 = -dx * seq->gx[2] + (1 - dy) * seq->gy[2];
			n1 = (1 - dx) * seq->gx[3] + (1 - dy) * seq->gy[3];
			ix1 = n0 + sx * (n1 - n0);

			p = ix0 + sy * (ix1 - ix0);

			if (perlin->uchar)
				q[x] = 128 * p + 128;
			else
				fq[x] = p;
		}
	}

	return 0;
}

static int
vips_perlin_build(VipsObject *object)
{
	VipsCreate *create = VIPS_CREATE(object);
	VipsPerlin *perlin = (VipsPerlin *) object;

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

	/* Be careful if width is a multiple of cell_size.
	 */
	perlin->cells_across =
		VIPS_ROUND_UP(perlin->width, perlin->cell_size) /
		perlin->cell_size;
	perlin->cells_down =
		VIPS_ROUND_UP(perlin->height, perlin->cell_size) /
		perlin->cell_size;

	vips_image_init_fields(create->out,
		perlin->width, perlin->height, 1,
		perlin->uchar ? VIPS_FORMAT_UCHAR : VIPS_FORMAT_FLOAT,
		VIPS_CODING_NONE, VIPS_INTERPRETATION_MULTIBAND,
		1.0, 1.0);
	if (vips_image_pipelinev(create->out, VIPS_DEMAND_STYLE_ANY, NULL) ||
		vips_image_generate(create->out,
			vips_perlin_start, vips_perlin_gen, vips_perlin_stop,
			perlin, NULL))
		return -1;

	return 0;
}

static void *
vips_perlin_make_tables(void *client)
{
	int i;

	for (i = 0; i < 256; i++) {
		double angle = 2 * VIPS_PI * i / 256.0;

		vips_perlin_cos[i] = cos(angle);
		vips_perlin_sin[i] = sin(angle);
	}

	return NULL;
}

static void
vips_perlin_class_init(VipsPerlinClass *class)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(class);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(class);

	static GOnce once = G_ONCE_INIT;

	VIPS_ONCE(&once, vips_perlin_make_tables, NULL);

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

	vobject_class->nickname = "perlin";
	vobject_class->description = _("make a perlin noise image");
	vobject_class->build = vips_perlin_build;

	VIPS_ARG_INT(class, "width", 2,
		_("Width"),
		_("Image width in pixels"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsPerlin, width),
		1, VIPS_MAX_COORD, 1);

	VIPS_ARG_INT(class, "height", 3,
		_("Height"),
		_("Image height in pixels"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsPerlin, height),
		1, VIPS_MAX_COORD, 1);

	VIPS_ARG_INT(class, "cell_size", 3,
		_("Cell size"),
		_("Size of Perlin cells"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsPerlin, cell_size),
		1, VIPS_MAX_COORD, 256);

	VIPS_ARG_BOOL(class, "uchar", 4,
		_("Uchar"),
		_("Output an unsigned char image"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsPerlin, uchar),
		FALSE);

	VIPS_ARG_INT(class, "seed", 5,
		_("Seed"),
		_("Random number seed"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsPerlin, seed),
		INT_MIN, INT_MAX, 0);
}

static void
vips_perlin_init(VipsPerlin *perlin)
{
	perlin->cell_size = 256;
	perlin->seed = UINT_MAX * g_random_double();
}

/**
 * vips_perlin:
 * @out: (out): output image
 * @width: horizontal size
 * @height: vertical size
 * @...: %NULL-terminated list of optional named arguments
 *
 * Optional arguments:
 *
 * * @cell_size: %gint, size of Perlin cells
 * * @uchar: output a uchar image
 *
 * Create a one-band float image of Perlin noise. See:
 *
 * https://en.wikipedia.org/wiki/Perlin_noise
 *
 * Use @cell_size to set the size of the cells from which the image is
 * constructed. The default is 256 x 256.
 *
 * If @width and @height are multiples of @cell_size, the image will tessellate.
 *
 * Normally, output pixels are #VIPS_FORMAT_FLOAT in the range [-1, +1]. Set
 * @uchar to output a uchar image with pixels in [0, 255].
 *
 * See also: vips_worley(), vips_fractsurf(), vips_gaussnoise().
 *
 * Returns: 0 on success, -1 on error
 */
int
vips_perlin(VipsImage **out, int width, int height, ...)
{
	va_list ap;
	int result;

	va_start(ap, height);
	result = vips_call_split("perlin", ap, out, width, height);
	va_end(ap);

	return result;
}
