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Ensure that the result of geom::simplify() is a valid geom or null #1722

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Merged
lonvia merged 1 commit into from
Jul 31, 2022
Merged

Ensure that the result of geom::simplify() is a valid geom or null #1722

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12 changes: 9 additions & 3 deletions src/geom-functions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -582,11 +582,17 @@ void simplify(geometry_t *output, geometry_t const &geom, double tolerance)
return;
}

output->set<linestring_t>();
auto &ls = output->set<linestring_t>();
output->set_srid(geom.srid());

boost::geometry::simplify(geom.get<linestring_t>(),
output->get<linestring_t>(), tolerance);
boost::geometry::simplify(geom.get<linestring_t>(), ls, tolerance);

// Linestrings with less then 2 nodes are invalid. Older boost::geometry
// versions will generate a "line" with two identical points which the
// second check finds.
if (ls.size() < 2 || ls[0] == ls[1]) {
output->reset();
}
}

geometry_t simplify(geometry_t const &geom, double tolerance)
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41 changes: 40 additions & 1 deletion tests/test-geom-linestrings.cpp
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Expand Up @@ -210,7 +210,7 @@ TEST_CASE("geom::simplify", "[NoDB]")

SECTION("large tolerance simplifies linestring")
{
auto const geom = geom::simplify(input, 2.0);
auto const geom = geom::simplify(input, 10.0);

REQUIRE(geom.is_linestring());
auto const &l = geom.get<geom::linestring_t>();
Expand All @@ -219,3 +219,42 @@ TEST_CASE("geom::simplify", "[NoDB]")
REQUIRE(l[1] == input.get<geom::linestring_t>()[5]);
}
}

TEST_CASE("geom::simplify of a loop", "[NoDB]")
{
geom::geometry_t const input{
geom::linestring_t{{0, 0}, {0, 1}, {1, 1}, {1, 0}, {0.1, 0.1}, {0, 0}}};

SECTION("small tolerance leaves linestring as is")
{
auto const geom = geom::simplify(input, 0.01);

REQUIRE(geom.is_linestring());
auto const &l = geom.get<geom::linestring_t>();
REQUIRE(l.size() == 6);
REQUIRE(l == input.get<geom::linestring_t>());
}

SECTION("medium tolerance simplifies linestring")
{
auto const geom = geom::simplify(input, 0.5);

REQUIRE(geom.is_linestring());
auto const &l = geom.get<geom::linestring_t>();
REQUIRE(l.size() == 5);

auto const &il = input.get<geom::linestring_t>();
REQUIRE(l[0] == il[0]);
REQUIRE(l[1] == il[1]);
REQUIRE(l[2] == il[2]);
REQUIRE(l[3] == il[3]);
REQUIRE(l[4] == il[5]);
}

SECTION("large tolerance breaks linestring, null geometry is returned")
{
auto const geom = geom::simplify(input, 10.0);

REQUIRE(geom.is_null());
}
}