Add missing files for #2996

git-svn-id: http://svn.osgeo.org/postgis/trunk@14449 b70326c6-7e19-0410-871a-916f4a2858ee

liblwgeom/cunit/cu_minimum_bounding_circle.c

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+/**********************************************************************
+ *
+ * PostGIS - Spatial Types for PostgreSQL
+ * http://postgis.net
+ * Copyright 2015 Daniel Baston
+ *
+ * This is free software; you can redistribute and/or modify it under
+ * the terms of the GNU General Public Licence. See the COPYING file.
+ *
+ **********************************************************************/
+
+#include "CUnit/Basic.h"
+#include "cu_tester.h"
+#include "../liblwgeom_internal.h"
+
+static void mbc_test(LWGEOM* g)
+{
+	LWBOUNDINGCIRCLE* result = lwgeom_calculate_mbc(g);
+	CU_ASSERT_TRUE(result != NULL);
+
+	LWPOINTITERATOR* it = lwpointiterator_create(g);
+
+	POINT2D p;
+	POINT4D p4;
+	while (lwpointiterator_next(it, &p4))
+	{
+		p.x = p4.x;
+		p.y = p4.y;
+
+		CU_ASSERT_TRUE(distance2d_pt_pt(result->center, &p) <= result->radius);
+	}
+
+	lwboundingcircle_destroy(result);
+	lwpointiterator_destroy(it);
+}
+
+static void basic_test(void)
+{
+	uint32_t i;
+
+	char* inputs[] =
+	{
+		"POLYGON((26426 65078,26531 65242,26075 65136,26096 65427,26426 65078))",
+		"POINT (17 253)",
+		"TRIANGLE ((0 0, 10 0, 10 10, 0 0))",
+		"LINESTRING (17 253, -44 28, 33 11, 26 44)",
+		"MULTIPOINT ((0 0), (0 0), (0 0), (0 0))",
+		"POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0))",
+		"LINESTRING (-48546889 37039202, -37039202 -48546889)"
+	};
+
+	for (i = 0; i < sizeof(inputs)/sizeof(LWGEOM*); i++)
+	{
+		LWGEOM* input = lwgeom_from_wkt(inputs[i], LW_PARSER_CHECK_NONE);
+		mbc_test(input);
+		lwgeom_free(input);
+	}
+
+}
+
+static void test_empty(void)
+{
+	LWGEOM* input = lwgeom_from_wkt("POINT EMPTY", LW_PARSER_CHECK_NONE);
+
+	LWBOUNDINGCIRCLE* result = lwgeom_calculate_mbc(input);
+	CU_ASSERT_TRUE(result == NULL);
+	
+	lwgeom_free(input);
+}
+
+/*
+ ** Used by test harness to register the tests in this file.
+ */
+void minimum_bounding_circle_suite_setup(void);
+void minimum_bounding_circle_suite_setup(void)
+{
+	CU_pSuite suite = CU_add_suite("minimum_bounding_circle", NULL, NULL);
+	PG_ADD_TEST(suite, basic_test);
+	PG_ADD_TEST(suite, test_empty);
+}

liblwgeom/lwboundingcircle.c

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+/**********************************************************************
+ *
+ * PostGIS - Spatial Types for PostgreSQL
+ * http://postgis.net
+ *
+ * Copyright 2015 Daniel Baston <dbaston@gmail.com>
+ *
+ * This is free software; you can redistribute and/or modify it under
+ * the terms of the GNU General Public Licence. See the COPYING file.
+ *
+ **********************************************************************/
+
+#include <string.h>
+#include "liblwgeom_internal.h"
+
+typedef struct {
+	const POINT2D* p1;
+	const POINT2D* p2;
+	const POINT2D* p3;
+} SUPPORTING_POINTS;
+
+static SUPPORTING_POINTS*
+supporting_points_create()
+{
+	SUPPORTING_POINTS* s = lwalloc(sizeof(SUPPORTING_POINTS));
+	s->p1 = NULL;
+	s->p2 = NULL;
+	s->p3 = NULL;
+
+	return s;
+}
+
+static void
+supporting_points_destroy(SUPPORTING_POINTS* s)
+{
+	lwfree(s);
+}
+
+static uint32_t
+num_supporting_points(SUPPORTING_POINTS* support)
+{
+	uint32_t N = 0;
+
+	if (support->p1 != NULL)
+		N++;
+	if (support->p2 != NULL)
+		N++;
+	if (support->p3 != NULL)
+		N++;
+
+	return N;
+}
+
+static int
+add_supporting_point(SUPPORTING_POINTS* support, const POINT2D* p)
+{
+	switch(num_supporting_points(support))
+	{
+		case 0: support->p1 = p;
+				break;
+		case 1: support->p2 = p;
+				break;
+		case 2: support->p3 = p;
+				break;
+		default: return LW_FAILURE;
+	}
+
+	return LW_SUCCESS;
+}
+
+static int
+point_inside_circle(const POINT2D* p, const LWBOUNDINGCIRCLE* c)
+{
+	if (!c)
+		return LW_FALSE;
+
+	if (distance2d_pt_pt(p, c->center) > c->radius)
+		return LW_FALSE;
+
+	return LW_TRUE;
+}
+
+static double
+det(double m00, double m01, double m10, double m11)
+{
+	return m00 * m11 - m01 * m10;
+}
+
+static void
+circumcenter(const POINT2D* a, const POINT2D* b, const POINT2D* c, POINT2D* result)
+{
+	double cx = c->x;
+	double cy = c->y;
+	double ax = a->x - cx;
+	double ay = a->y - cy;
+	double bx = b->x - cx;
+	double by = b->y - cy;
+
+	double denom = 2 * det(ax, ay, bx, by);
+	double numx = det(ay, ax * ax + ay * ay, by, bx * bx + by * by);
+	double numy = det(ax, ax * ax + ay * ay, bx, bx * bx + by * by);
+
+	result->x = cx - numx / denom;
+	result->y = cy + numy / denom;
+}
+
+static void
+calculate_mbc_1(const SUPPORTING_POINTS* support, LWBOUNDINGCIRCLE* mbc)
+{
+	mbc->radius = 0;
+	mbc->center->x = support->p1->x;
+	mbc->center->y = support->p1->y;
+}
+
+static void
+calculate_mbc_2(const SUPPORTING_POINTS* support, LWBOUNDINGCIRCLE* mbc)
+{
+	double d1, d2;
+
+	mbc->center->x = 0.5*(support->p1->x + support->p2->x);
+	mbc->center->y = 0.5*(support->p1->y + support->p2->y);
+
+	d1 = distance2d_pt_pt(mbc->center, support->p1);
+	d2 = distance2d_pt_pt(mbc->center, support->p2);
+
+	mbc->radius = FP_MAX(d1, d2);
+}
+
+static void
+calculate_mbc_3(const SUPPORTING_POINTS* support, LWBOUNDINGCIRCLE* mbc)
+{
+	double d1, d2, d3;
+	circumcenter(support->p1, support->p2, support->p3, mbc->center);
+
+	d1 = distance2d_pt_pt(mbc->center, support->p1);
+	d2 = distance2d_pt_pt(mbc->center, support->p2);
+	d3 = distance2d_pt_pt(mbc->center, support->p3);
+
+	mbc->radius = FP_MAX(FP_MAX(d1, d2), d3);
+}
+
+static int
+calculate_mbc_from_support(SUPPORTING_POINTS* support, LWBOUNDINGCIRCLE* mbc)
+{
+	switch(num_supporting_points(support))
+	{
+		case 0: break;
+		case 1: calculate_mbc_1(support, mbc);
+				break;
+		case 2: calculate_mbc_2(support, mbc);
+				break;
+		case 3: calculate_mbc_3(support, mbc);
+				break;
+		default: return LW_FAILURE;
+	}
+
+	return LW_SUCCESS;
+}
+
+static int
+calculate_mbc(const POINT2D** points, uint32_t max_n, SUPPORTING_POINTS* support, LWBOUNDINGCIRCLE* mbc)
+{
+	uint32_t i;
+
+	if(!calculate_mbc_from_support(support, mbc))
+	{
+		return LW_FAILURE;
+	}
+
+	if (num_supporting_points(support) == 3)
+	{
+		/* If we're entering the function with three supporting points already, our circle
+		 * is already fully constrained - we couldn't add another supporting point if we
+		 * needed to. So, there's no point in proceeding further.  Welzl (1991) provides 
+		 * a much better explanation of why this works.
+		 * */
+		return LW_SUCCESS;
+	}
+
+	for (i = 0; i < max_n; i++)
+	{
+		if (!point_inside_circle(points[i], mbc))
+		{
+			/* We've run into a point that isn't inside our circle.  To fix this, we'll
+			 * go back in time, and re-run the algorithm for each point we've seen so
+			 * far, with the constraint that the current point must be on the boundary
+			 * of the circle.  Then, we'll continue on in this loop with the modified
+			 * circle that by definition includes the current point. */
+			SUPPORTING_POINTS next_support;
+			memcpy(&next_support, support, sizeof(SUPPORTING_POINTS));
+
+			add_supporting_point(&next_support, points[i]);
+			if (!calculate_mbc(points, i, &next_support, mbc))
+			{
+				return LW_FAILURE;
+			}
+		}
+	}
+
+	return LW_SUCCESS;
+}
+
+static LWBOUNDINGCIRCLE*
+lwboundingcircle_create()
+{
+	LWBOUNDINGCIRCLE* c = lwalloc(sizeof(LWBOUNDINGCIRCLE));
+	c->center = lwalloc(sizeof(POINT2D));
+
+	c->radius = 0.0;
+	c->center->x = 0.0;
+	c->center->y = 0.0;
+
+	return c;
+}
+
+void
+lwboundingcircle_destroy(LWBOUNDINGCIRCLE* c)
+{
+	lwfree(c->center);
+	lwfree(c);
+}
+
+LWBOUNDINGCIRCLE*
+lwgeom_calculate_mbc(const LWGEOM* g)
+{
+	SUPPORTING_POINTS* support;
+	LWBOUNDINGCIRCLE* result;
+	LWPOINTITERATOR* it;
+	uint32_t num_points;
+	POINT2D** points;
+	POINT4D p;
+	uint32_t i;
+	int success;
+
+	if(g == NULL || lwgeom_is_empty(g))
+		return LW_FAILURE;
+
+	num_points = lwgeom_count_vertices(g);
+	it = lwpointiterator_create(g);
+	points = lwalloc(num_points * sizeof(POINT2D*));
+	for (i = 0; i < num_points; i++)
+	{
+		if(!lwpointiterator_next(it, &p))
+		{
+			uint32_t j;
+			for (j = 0; j < i; j++)
+			{
+				lwfree(points[j]);
+			}
+			lwpointiterator_destroy(it);
+			lwfree(points);
+			return LW_FAILURE;
+		}
+
+		points[i] = lwalloc(sizeof(POINT2D));
+		points[i]->x = p.x;
+		points[i]->y = p.y;
+	}
+	lwpointiterator_destroy(it);
+
+	support = supporting_points_create();
+	result = lwboundingcircle_create();
+	/* Technically, a randomized algorithm would demand that we shuffle the input points
+	 * before we call calculate_mbc().  However, we make the (perhaps poor) assumption that 
+	 * the order we happen to find the points is as good as random, or close enough.
+	 * */
+	success = calculate_mbc((const POINT2D**) points, num_points, support, result);
+
+	for (i = 0; i < num_points; i++)
+	{
+		lwfree(points[i]);
+	}
+	lwfree(points);
+	supporting_points_destroy(support);
+
+	if (!success)
+		return NULL;
+
+	return result;
+}

regress/minimum_bounding_circle.sql

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+SELECT 't1', ST_MinimumBoundingCircle(NULL::geometry) IS NULL;
+SELECT 't2', ST_Equals(ST_MinimumBoundingCircle('POINT EMPTY'), 'POLYGON EMPTY'::geometry);
+SELECT 't3', ST_SRID(ST_MinimumBoundingCircle('SRID=32611;POINT(4021690.58034526 6040138.01373556)')) = 32611;
+SELECT 't4', ST_SRID(center) = 32611 FROM ST_MinimumBoundingRadius('SRID=32611;POINT(4021690.58034526 6040138.01373556)');
+SELECT 't5', ST_Equals(center, 'POINT EMPTY') AND radius = 0 FROM ST_MinimumBoundingRadius('GEOMETRYCOLLECTION EMPTY');
+SELECT 't6', ST_Equals(center, 'POINT (0 0.5)') AND radius = 0.5 FROM ST_MinimumBoundingRadius('MULTIPOINT ((0 0 0), (0 1 1))');

regress/minimum_bounding_circle_expected

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+t1|t
+t2|t
+t3|t
+t4|t
+t5|t
+t6|t