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Detect longitude wraparound only if it reduces self-intersections

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This commit is contained in:
Erica Fischer
2024-02-20 22:08:59 -08:00
parent 2b6630c42c
commit 5d1c01d4b9
3 changed files with 114 additions and 27 deletions
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serial.cpp
+65 -27
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@@ -298,9 +298,71 @@ serial_feature deserialize_feature(std::string const &geoms, unsigned z, unsigne
}
static long long scale_geometry(struct serialization_state *sst, long long *bbox, drawvec &geom) {
long long offset = 0;
long long prev = 0;
bool has_prev = false;
if (additional[A_DETECT_WRAPAROUND]) {
drawvec adjusted = geom;
std::vector<size_t> jumps;
long long offset = 0;
long long prev = 0;
bool has_prev = false;
for (size_t i = 0; i < geom.size(); i++) {
if (geom[i].op == VT_LINETO) {
long long x = geom[i].x;
x += offset;
if (has_prev) {
// jumps at least 180° in either direction
if (x - prev > (1LL << 31)) {
offset -= 1LL << 32;
x -= 1LL << 32;
jumps.push_back(i);
} else if (prev - x > (1LL << 31)) {
offset += 1LL << 32;
x += 1LL << 32;
jumps.push_back(i);
}
}
adjusted[i].x = x;
has_prev = true;
prev = x;
} else {
offset = 0;
prev = geom[i].x;
}
}
// count whether making these adjustments resulted in
// more or less self-intersections than in the original
size_t orig_bad = 0;
size_t adjusted_bad = 0;
for (auto i : jumps) {
for (size_t j = 1; j < geom.size(); j++) {
if (geom[j].op == VT_LINETO && j != i) {
auto before = get_line_intersection(geom[i - 1].x, geom[i - 1].y, geom[i].x, geom[i].y,
geom[j - 1].x, geom[j - 1].y, geom[j].x, geom[j].y);
auto after = get_line_intersection(adjusted[i - 1].x, adjusted[i - 1].y, adjusted[i].x, adjusted[i].y,
adjusted[j - 1].x, adjusted[j - 1].y, adjusted[j].x, adjusted[j].y);
if (before.first > 0 && before.first < 1) {
orig_bad++;
}
if (after.first > 0 && after.first < 1) {
adjusted_bad++;
}
}
}
}
if (orig_bad > adjusted_bad) {
geom = std::move(adjusted);
}
}
double scale = 1.0 / (1 << geometry_scale);
for (size_t i = 0; i < geom.size(); i++) {
@@ -308,30 +370,6 @@ static long long scale_geometry(struct serialization_state *sst, long long *bbox
long long x = geom[i].x;
long long y = geom[i].y;
if (additional[A_DETECT_WRAPAROUND]) {
if (geom[i].op == VT_LINETO) {
x += offset;
if (has_prev) {
// jumps at least 180° but not exactly 360°,
// which in some data sets is an intentional
// line across the world
if (x - prev > (1LL << 31) && x - prev != (1LL << 32)) {
offset -= 1LL << 32;
x -= 1LL << 32;
} else if (prev - x > (1LL << 31) && prev - x != (1LL << 32)) {
offset += 1LL << 32;
x += 1LL << 32;
}
}
has_prev = true;
prev = x;
} else {
offset = 0;
prev = x;
}
}
if (x < bbox[0]) {
bbox[0] = x;
}