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#pragma once
#include <mapbox/geojsonvt/types.hpp>
namespace mapbox {
namespace geojsonvt {
namespace detail {
template <uint8_t I>
class clipper {
public:
const double k1;
const double k2;
vt_geometry operator()(const vt_point& point) const {
return point;
}
vt_geometry operator()(const vt_multi_point& points) const {
vt_multi_point part;
for (const auto& p : points) {
const double ak = get<I>(p);
if (ak >= k1 && ak <= k2)
part.push_back(p);
}
return part;
}
vt_geometry operator()(const vt_line_string& line) const {
vt_multi_line_string parts;
clipLine(line, parts);
if (parts.size() == 1)
return parts[0];
else
return parts;
}
vt_geometry operator()(const vt_multi_line_string& lines) const {
vt_multi_line_string parts;
for (const auto& line : lines) {
clipLine(line, parts);
}
if (parts.size() == 1)
return parts[0];
else
return parts;
}
vt_geometry operator()(const vt_polygon& polygon) const {
vt_polygon result;
for (const auto& ring : polygon) {
const auto new_ring = clipRing(ring);
if (!new_ring.empty())
result.push_back(new_ring);
}
return result;
}
vt_geometry operator()(const vt_multi_polygon& polygons) const {
vt_multi_polygon result;
for (const auto& polygon : polygons) {
vt_polygon p;
for (const auto& ring : polygon) {
const auto new_ring = clipRing(ring);
if (!new_ring.empty())
p.push_back(new_ring);
}
if (!p.empty())
result.push_back(p);
}
return result;
}
vt_geometry operator()(const vt_geometry_collection& geometries) const {
vt_geometry_collection result;
for (const auto& geometry : geometries) {
vt_geometry::visit(geometry,
[&](const auto& g) { result.push_back(this->operator()(g)); });
}
return result;
}
private:
vt_line_string newSlice(vt_multi_line_string& parts, vt_line_string& slice, double dist) const {
if (!slice.empty()) {
slice.dist = dist;
parts.push_back(std::move(slice));
}
return {};
}
void clipLine(const vt_line_string& line, vt_multi_line_string& slices) const {
const double dist = line.dist;
const size_t len = line.size();
if (len < 2)
return;
vt_line_string slice;
for (size_t i = 0; i < (len - 1); ++i) {
const auto& a = line[i];
const auto& b = line[i + 1];
const double ak = get<I>(a);
const double bk = get<I>(b);
if (ak < k1) {
if (bk > k2) { // ---|-----|-->
slice.push_back(intersect<I>(a, b, k1));
slice.push_back(intersect<I>(a, b, k2));
slice = newSlice(slices, slice, dist);
} else if (bk >= k1) { // ---|--> |
slice.push_back(intersect<I>(a, b, k1));
if (i == len - 2)
slice.push_back(b); // last point
}
} else if (ak > k2) {
if (bk < k1) { // <--|-----|---
slice.push_back(intersect<I>(a, b, k2));
slice.push_back(intersect<I>(a, b, k1));
slice = newSlice(slices, slice, dist);
} else if (bk <= k2) { // | <--|---
slice.push_back(intersect<I>(a, b, k2));
if (i == len - 2)
slice.push_back(b); // last point
}
} else {
slice.push_back(a);
if (bk < k1) { // <--|--- |
slice.push_back(intersect<I>(a, b, k1));
slice = newSlice(slices, slice, dist);
} else if (bk > k2) { // | ---|-->
slice.push_back(intersect<I>(a, b, k2));
slice = newSlice(slices, slice, dist);
} else if (i == len - 2) { // | --> |
slice.push_back(b);
}
}
}
// add the final slice
newSlice(slices, slice, dist);
}
vt_linear_ring clipRing(const vt_linear_ring& ring) const {
const size_t len = ring.size();
vt_linear_ring slice;
slice.area = ring.area;
if (len < 2)
return slice;
for (size_t i = 0; i < (len - 1); ++i) {
const auto& a = ring[i];
const auto& b = ring[i + 1];
const double ak = get<I>(a);
const double bk = get<I>(b);
if (ak < k1) {
if (bk >= k1) {
slice.push_back(intersect<I>(a, b, k1)); // ---|--> |
if (bk > k2) // ---|-----|-->
slice.push_back(intersect<I>(a, b, k2));
else if (i == len - 2)
slice.push_back(b); // last point
}
} else if (ak > k2) {
if (bk <= k2) { // | <--|---
slice.push_back(intersect<I>(a, b, k2));
if (bk < k1) // <--|-----|---
slice.push_back(intersect<I>(a, b, k1));
else if (i == len - 2)
slice.push_back(b); // last point
}
} else {
slice.push_back(a);
if (bk < k1) // <--|--- |
slice.push_back(intersect<I>(a, b, k1));
else if (bk > k2) // | ---|-->
slice.push_back(intersect<I>(a, b, k2));
// | --> |
}
}
// close the polygon if its endpoints are not the same after clipping
if (!slice.empty()) {
const auto& first = slice.front();
const auto& last = slice.back();
if (first != last) {
slice.push_back(first);
}
}
return slice;
}
};
/* clip features between two axis-parallel lines:
* | |
* ___|___ | /
* / | \____|____/
* | |
*/
template <uint8_t I>
inline vt_features clip(const vt_features& features,
const double k1,
const double k2,
const double minAll,
const double maxAll) {
if (minAll >= k1 && maxAll <= k2) // trivial accept
return features;
if (minAll > k2 || maxAll < k1) // trivial reject
return {};
vt_features clipped;
for (const auto& feature : features) {
const auto& geom = feature.geometry;
const auto& props = feature.properties;
const auto& id = feature.id;
const double min = get<I>(feature.bbox.min);
const double max = get<I>(feature.bbox.max);
if (min >= k1 && max <= k2) { // trivial accept
clipped.push_back(feature);
} else if (min > k2 || max < k1) { // trivial reject
continue;
} else {
clipped.emplace_back(vt_geometry::visit(geom, clipper<I>{ k1, k2 }), props, id);
}
}
return clipped;
}
} // namespace detail
} // namespace geojsonvt
} // namespace mapbox
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