Added methods for calculating length and area.

This commit exposes the following methods: - tg_line_length - tg_ring_perimeter - tg_ring_area See #5
tidwall · Oct 4, 2023 · f205537 · f205537
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Showing 5 changed files with 44 additions and 6 deletions.
diff --git a/docs/API.md b/docs/API.md
@@ -344,6 +344,8 @@ tg_geom_interects((struct tg_geom*)ring, geom);
 - [tg_ring_nearest_segment()](#group___ring_funcs_1ga716e10054b4bda84efb259d57aff5015)
 - [tg_ring_line_search()](#group___ring_funcs_1gabee40f4a66c2ebb4516a9f980ff5d998)
 - [tg_ring_ring_search()](#group___ring_funcs_1gacd2c483213d8110c9373e8e47bd9f49e)
+- [tg_ring_area()](#group___ring_funcs_1gabe14408b3ad596ed14b4ce698c2e7826)
+- [tg_ring_perimeter()](#group___ring_funcs_1ga0d063ecfef895e21f6d7520db05d302e)
 
 
 <a name='group___line_funcs'></a>
@@ -379,6 +381,7 @@ tg_geom_interects((struct tg_geom*)line, geom);
 - [tg_line_index_level_rect()](#group___line_funcs_1gacc18e4ddb48ccc717f61f298fd6ae970)
 - [tg_line_nearest_segment()](#group___line_funcs_1gaa85835e9619ba7d8557fda3335a0353a)
 - [tg_line_line_search()](#group___line_funcs_1gafef8ca6e5381e93d4c4952343597c0e1)
+- [tg_line_length()](#group___line_funcs_1ga994796f0088c82bb0672d84f1a1ce9d1)
 
 
 <a name='group___poly_funcs'></a>
@@ -3834,6 +3837,22 @@ Iterates over all segments in ring A that intersect with segments in ring B.
 
 
 
+<a name='group___ring_funcs_1gabe14408b3ad596ed14b4ce698c2e7826'></a>
+## tg_ring_area()
+```c
+double tg_ring_area(const struct tg_ring *ring);
+```
+Calculate the area of a ring. 
+
+
+<a name='group___ring_funcs_1ga0d063ecfef895e21f6d7520db05d302e'></a>
+## tg_ring_perimeter()
+```c
+double tg_ring_perimeter(const struct tg_ring *ring);
+```
+Calculate the perimeter length of a ring. 
+
+
 <a name='group___line_funcs_1ga7f834a7213c8d87d8b7c7117bdf8bf63'></a>
 ## tg_line_new()
 ```c
@@ -4326,6 +4345,14 @@ Iterates over all segments in line A that intersect with segments in line B.
 
 
 
+<a name='group___line_funcs_1ga994796f0088c82bb0672d84f1a1ce9d1'></a>
+## tg_line_length()
+```c
+double tg_line_length(const struct tg_line *line);
+```
+Calculate the length of a line. 
+
+
 <a name='group___poly_funcs_1ga56c2615488ca202baa944c85c20a40f1'></a>
 ## tg_poly_new()
 ```c

diff --git a/tests/test_line.c b/tests/test_line.c
@@ -144,7 +144,7 @@ void test_line_various() {
     assert(tg_line_memsize(NULL) == 0);
     tg_line_free(line2);
     assert(!tg_line_copy(0));
-
+    assert(tg_line_length(LINE(u1)) == 30.0);
 }
 
 int main(int argc, char **argv) {

diff --git a/tests/test_ring.c b/tests/test_ring.c
@@ -1354,6 +1354,8 @@ void test_ring_various() {
     assert(tg_ring_contains_line(0, (struct tg_line*)RING(az), 0, 0) == 0);
     assert(tg_ring_contains_line(0, 0, 0, 0) == 0);
 
+    assert(tg_ring_perimeter(RING(u1)) == 40.0);
+    assert(tg_ring_area(RING(u1)) == 100.0);
 }
 
 void test_ring_pip(void) {

diff --git a/tg.c b/tg.c
@@ -13511,13 +13511,15 @@ struct tg_geom *tg_parse_hex(const char *hex) {
     return tg_parse_hexn_ix(hex, hex?strlen(hex):0, TG_DEFAULT);
 }
 
-static double ring_area(const struct tg_ring *ring) {
+/// Calculate the area of a ring.
+double tg_ring_area(const struct tg_ring *ring) {
     if (tg_ring_empty(ring)) return 0;
     // The ring area has already been calculated by process_points.
     return ring->area;
 }
 
-static double ring_perimeter(const struct tg_ring *ring) {
+/// Calculate the perimeter length of a ring.
+double tg_ring_perimeter(const struct tg_ring *ring) {
     if (tg_ring_empty(ring)) return 0;
     int nsegs = tg_ring_num_segments(ring);
     double perim = 0;
@@ -13538,8 +13540,8 @@ double tg_ring_polsby_popper_score(const struct tg_ring *ring) {
     // and all other shapes will be smaller. Itty bitty scores mean the
     // polygon is really something nuts or has bad data.
     double score = 0.0;
-    double perim = ring_perimeter(ring);
-    double area = ring_area(ring);
+    double perim = tg_ring_perimeter(ring);
+    double area = tg_ring_area(ring);
     if (perim > 0) {
         score = (area * M_PI * 4) / (perim * perim);
     }
@@ -14263,3 +14265,8 @@ void tg_geom_search(const struct tg_geom *geom, struct tg_rect rect,
         multi_index_search(multi, rect, 0, 0, iter, udata);
     }
 }
+
+/// Calculate the length of a line.
+double tg_line_length(const struct tg_line *line) {
+    return tg_ring_perimeter((struct tg_ring*)line);
+}
diff --git a/tg.h b/tg.h
@@ -268,7 +268,8 @@ void tg_ring_ring_search(const struct tg_ring *a, const struct tg_ring *b,
     bool (*iter)(struct tg_segment aseg, int aidx, struct tg_segment bseg, 
         int bidx, void *udata),
     void *udata);
-
+double tg_ring_area(const struct tg_ring *ring);
+double tg_ring_perimeter(const struct tg_ring *ring);
 /// @}
 
 /// @defgroup LineFuncs Line functions
@@ -308,6 +309,7 @@ void tg_line_line_search(const struct tg_line *a, const struct tg_line *b,
     bool (*iter)(struct tg_segment aseg, int aidx, struct tg_segment bseg, 
         int bidx, void *udata),
     void *udata);
+double tg_line_length(const struct tg_line *line);
 /// @}
 
 /// @defgroup PolyFuncs Polygon functions