Added a Ramer-Douglas-Peucker line/polygon simplification algorithm.

Author: derickr

config.m4

@@ -1,62 +1,9 @@
 dnl $Id$
 dnl config.m4 for extension geospatial
 
-dnl Comments in this file start with the string 'dnl'.
-dnl Remove where necessary. This file will not work
-dnl without editing.
-
-dnl If your extension references something external, use with:
-
-dnl PHP_ARG_WITH(geospatial, for geospatial support,
-dnl Make sure that the comment is aligned:
-dnl [  --with-geospatial             Include geospatial support])
-
-dnl Otherwise use enable:
-
 PHP_ARG_ENABLE(geospatial, whether to enable geospatial support,
 [  --enable-geospatial           Enable geospatial support])
 
 if test "$PHP_GEOSPATIAL" != "no"; then
-  dnl Write more examples of tests here...
-
-  dnl # --with-geospatial -> check with-path
-  dnl SEARCH_PATH="/usr/local /usr"     # you might want to change this
-  dnl SEARCH_FOR="/include/geospatial.h"  # you most likely want to change this
-  dnl if test -r $PHP_GEOSPATIAL/$SEARCH_FOR; then # path given as parameter
-  dnl   GEOSPATIAL_DIR=$PHP_GEOSPATIAL
-  dnl else # search default path list
-  dnl   AC_MSG_CHECKING([for geospatial files in default path])
-  dnl   for i in $SEARCH_PATH ; do
-  dnl     if test -r $i/$SEARCH_FOR; then
-  dnl       GEOSPATIAL_DIR=$i
-  dnl       AC_MSG_RESULT(found in $i)
-  dnl     fi
-  dnl   done
-  dnl fi
-  dnl
-  dnl if test -z "$GEOSPATIAL_DIR"; then
-  dnl   AC_MSG_RESULT([not found])
-  dnl   AC_MSG_ERROR([Please reinstall the geospatial distribution])
-  dnl fi
-
-  dnl # --with-geospatial -> add include path
-  dnl PHP_ADD_INCLUDE($GEOSPATIAL_DIR/include)
-
-  dnl # --with-geospatial -> check for lib and symbol presence
-  dnl LIBNAME=geospatial # you may want to change this
-  dnl LIBSYMBOL=geospatial # you most likely want to change this 
-
-  dnl PHP_CHECK_LIBRARY($LIBNAME,$LIBSYMBOL,
-  dnl [
-  dnl   PHP_ADD_LIBRARY_WITH_PATH($LIBNAME, $GEOSPATIAL_DIR/lib, GEOSPATIAL_SHARED_LIBADD)
-  dnl   AC_DEFINE(HAVE_GEOSPATIALLIB,1,[ ])
-  dnl ],[
-  dnl   AC_MSG_ERROR([wrong geospatial lib version or lib not found])
-  dnl ],[
-  dnl   -L$GEOSPATIAL_DIR/lib -lm
-  dnl ])
-  dnl
-  dnl PHP_SUBST(GEOSPATIAL_SHARED_LIBADD)
-
-  PHP_NEW_EXTENSION(geospatial, geospatial.c, $ext_shared)
+  PHP_NEW_EXTENSION(geospatial, geospatial.c geo_array.c, $ext_shared)
 fi

geo_array.c

@@ -0,0 +1,24 @@
+#include <stdlib.h>
+
+#include "geo_array.h"
+
+geo_array *geo_array_ctor(int element_count)
+{
+	geo_array *tmp;
+
+	tmp = malloc(sizeof(geo_array));
+	tmp->count = element_count;
+	tmp->status = calloc(1, element_count);
+	tmp->x = (double*) calloc(1, element_count * sizeof(double));
+	tmp->y = (double*) calloc(1, element_count * sizeof(double));
+
+	return tmp;
+}
+	
+void geo_array_dtor(geo_array *points)
+{
+	free(points->status);
+	free(points->x);
+	free(points->y);
+	free(points);
+}

geo_array.h

@@ -0,0 +1,9 @@
+typedef struct geo_array {
+	double  *x;
+	double  *y;
+	char    *status;
+	int      count;
+} geo_array;
+
+geo_array *geo_array_ctor(int element_count);
+void geo_array_dtor(geo_array *points);

geospatial.c

@@ -27,6 +27,7 @@
 #include "php_ini.h"
 #include "ext/standard/info.h"
 #include "php_geospatial.h"
+#include "geo_array.h"
 
 ZEND_BEGIN_ARG_INFO_EX(haversine_args, 0, 0, 4)
 	ZEND_ARG_INFO(0, fromLatitude)
@@ -81,6 +82,11 @@ ZEND_BEGIN_ARG_INFO_EX(decimal_to_dms_args, 0, 0, 2)
 	ZEND_ARG_INFO(0, coordinate)
 ZEND_END_ARG_INFO()
 
+ZEND_BEGIN_ARG_INFO_EX(rdp_simplify_args, 0, 0, 2)
+	ZEND_ARG_INFO(0, pointsArray)
+	ZEND_ARG_INFO(0, epsilon)
+ZEND_END_ARG_INFO()
+
 /* {{{ geospatial_functions[]
  *
  * Every user visible function must have an entry in geospatial_functions[].
@@ -94,6 +100,7 @@ const zend_function_entry geospatial_functions[] = {
 	PHP_FE(transform_datum, transform_datum_args)
 	PHP_FE(dms_to_decimal, dms_to_decimal_args)
 	PHP_FE(decimal_to_dms, decimal_to_dms_args)
+	PHP_FE(rdp_simplify, rdp_simplify_args)
 	/* End of functions */
 	{ NULL, NULL, NULL }
 };
@@ -449,6 +456,7 @@ PHP_FUNCTION(transform_datum)
 	long from_reference_ellipsoid, to_reference_ellipsoid;
 	geo_cartesian point, converted_point;
 	geo_lat_long polar;
+
 	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ddll", &latitude, &longitude, &from_reference_ellipsoid, &to_reference_ellipsoid) == FAILURE) {
 		return;
 	}
@@ -529,6 +537,142 @@ PHP_FUNCTION(fraction_along_gc_line)
 }
 /* }}} */
 
+geo_array *geo_hashtable_to_array(zval *array)
+{
+	geo_array *tmp;
+	int element_count;
+	HashPosition pos;
+	zval **entry;
+	zval  **z_lon, **z_lat;
+	int   i = 0;
+
+	element_count = zend_hash_num_elements(Z_ARRVAL_P(array));
+	tmp = geo_array_ctor(element_count);
+
+	zend_hash_internal_pointer_reset_ex(Z_ARRVAL_P(array), &pos);
+	while (zend_hash_get_current_data_ex(Z_ARRVAL_P(array), (void **)&entry, &pos) == SUCCESS) {
+
+		if (Z_TYPE_PP(entry) != IS_ARRAY) {
+			goto failure;
+		}
+		if (zend_hash_num_elements(Z_ARRVAL_PP(entry)) != 2)
+		{
+			goto failure;
+		}
+		if (zend_hash_index_find(HASH_OF(*entry), 0, (void**) &z_lon) != SUCCESS) {
+			return 0;
+		}
+		if (zend_hash_index_find(HASH_OF(*entry), 1, (void**) &z_lat) != SUCCESS) {
+			return 0;
+		}
+		convert_to_double_ex(z_lon);
+		convert_to_double_ex(z_lat);
+
+		tmp->x[i] = Z_DVAL_PP(z_lon);
+		tmp->y[i] = Z_DVAL_PP(z_lat);
+		tmp->status[i] = 1;
+
+		zend_hash_move_forward_ex(Z_ARRVAL_P(array), &pos);
+		i++;
+	}
+
+	return tmp;
+
+failure:
+	geo_array_dtor(tmp);
+	return NULL;
+}
+
+double rdp_find_perpendicular_distable(double pX, double pY, double p1X, double p1Y, double p2X, double p2Y)
+{
+	double slope, intercept, result;
+
+	if (p1X == p2X) {
+		return fabs(pX - p1X);
+	} else {
+		slope = (p2Y - p1Y) / (p2X - p1X);
+		intercept = p1Y - (slope * p1X);
+		result = fabs(slope * pX - pY + intercept) / sqrt(pow(slope, 2) + 1);
+		return result;
+	}
+}
+
+void rdp_simplify(geo_array *points, double epsilon, int start, int end)
+{
+	double firstX = points->x[start];
+	double firstY = points->y[start];
+	double lastX = points->x[end];
+	double lastY = points->y[end];
+	int    index = -1;
+	double dist  = 0.0, current_dist;
+	int    i;
+
+	if (end - start < 2) {
+		return;
+	}
+
+	for (i = start + 1; i < end; i++) {
+		if (!points->status[i]) {
+			continue;
+		}
+
+		current_dist = rdp_find_perpendicular_distable(points->x[i], points->y[i], firstX, firstY, lastX, lastY);
+
+		if (current_dist > dist) {
+			dist = current_dist;
+			index = i;
+		}
+	}
+
+	if (dist > epsilon) {
+		rdp_simplify(points, epsilon, start, index);
+		rdp_simplify(points, epsilon, index, end);
+
+		return;
+	} else {
+		for (i = start + 1; i < end; i++) {
+			points->status[i] = 0;
+		}
+		return;
+	}
+}
+
+/* {{{ proto array rdp_simplify(array points, float epsilon)
+   Simplifies a 2D dimensional line according to the Ramer-Douglas-Peucker algorithm */
+PHP_FUNCTION(rdp_simplify)
+{
+	zval      *points_array;
+	double     epsilon;
+	geo_array *points;
+	int        i;
+	zval      *pair;
+
+	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "zd", &points_array, &epsilon) == FAILURE) {
+		return;
+	}
+
+	if (!Z_TYPE_P(points_array) == IS_ARRAY) {
+		return;
+	}
+
+	array_init(return_value);
+
+	points = geo_hashtable_to_array(points_array);
+	rdp_simplify(points, epsilon, 0, points->count - 1);
+	for (i = 0; i < points->count; i++) {
+		if (points->status[i]) {
+			MAKE_STD_ZVAL(pair);
+			array_init(pair);
+			add_next_index_double(pair, points->x[i]);
+			add_next_index_double(pair, points->y[i]);
+			add_next_index_zval(return_value, pair);
+		}
+	}
+
+	geo_array_dtor(points);
+}
+/* }}} */
+
 /*
  * Local variables:
  * tab-width: 4

php_geospatial.h

@@ -128,6 +128,7 @@ PHP_FUNCTION(cartesian_to_polar);
 PHP_FUNCTION(transform_datum);
 PHP_FUNCTION(dms_to_decimal);
 PHP_FUNCTION(decimal_to_dms);
+PHP_FUNCTION(rdp_simplify);
 
 #endif	/* PHP_GEOSPATIAL_H */