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Don't let line simplification reduce a polygon ring to below 3 points

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Eric Fischer
2016-11-14 11:22:21 -08:00
parent 32aa653082
commit 9ea29601ab
16 changed files with 460 additions and 459 deletions
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geometry.cpp
+6 -5
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@@ -893,7 +893,7 @@ static double square_distance_from_line(long long point_x, long long point_y, lo
}
// https://github.com/Project-OSRM/osrm-backend/blob/733d1384a40f/Algorithms/DouglasePeucker.cpp
static void douglas_peucker(drawvec &geom, int start, int n, double e) {
static void douglas_peucker(drawvec &geom, int start, int n, double e, size_t kept, size_t retain) {
e = e * e;
std::stack<int> recursion_stack;
@@ -928,15 +928,16 @@ static void douglas_peucker(drawvec &geom, int start, int n, double e) {
double distance = std::fabs(temp_dist);
if (distance > e && distance > max_distance) {
if ((distance > e || kept < retain) && distance > max_distance) {
farthest_element_index = i;
max_distance = distance;
}
}
if (max_distance > e) {
if (max_distance >= 0) {
// mark idx as necessary
geom[start + farthest_element_index].necessary = 1;
kept++;
if (1 < farthest_element_index - first) {
recursion_stack.push(first);
@@ -984,7 +985,7 @@ drawvec impose_tile_boundaries(drawvec &geom, long long extent) {
return out;
}
drawvec simplify_lines(drawvec &geom, int z, int detail, bool mark_tile_bounds, double simplification) {
drawvec simplify_lines(drawvec &geom, int z, int detail, bool mark_tile_bounds, double simplification, size_t retain) {
int res = 1 << (32 - detail - z);
long long area = 1LL << (32 - z);
@@ -1015,7 +1016,7 @@ drawvec simplify_lines(drawvec &geom, int z, int detail, bool mark_tile_bounds,
geom[j - 1].necessary = 1;
if (j - i > 1) {
douglas_peucker(geom, i, j - i, res * simplification);
douglas_peucker(geom, i, j - i, res * simplification, 2, retain);
}
i = j - 1;
}