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/*
* Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above
* copyright notice, this list of conditions and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "FloatPolygon.h"
#include <wtf/HexNumber.h>
#include <wtf/MathExtras.h>
namespace WebCore {
namespace FloatPolygonInternal {
static inline float determinant(const FloatSize& a, const FloatSize& b)
{
return a.width() * b.height() - a.height() * b.width();
}
}
static inline bool areCollinearPoints(const FloatPoint& p0, const FloatPoint& p1, const FloatPoint& p2)
{
return !FloatPolygonInternal::determinant(p1 - p0, p2 - p0);
}
static inline bool areCoincidentPoints(const FloatPoint& p0, const FloatPoint& p1)
{
return p0.x() == p1.x() && p0.y() == p1.y();
}
static inline unsigned nextVertexIndex(unsigned vertexIndex, unsigned nVertices, bool clockwise)
{
return ((clockwise) ? vertexIndex + 1 : vertexIndex - 1 + nVertices) % nVertices;
}
static unsigned findNextEdgeVertexIndex(const FloatPolygon& polygon, unsigned vertexIndex1, bool clockwise)
{
unsigned nVertices = polygon.numberOfVertices();
unsigned vertexIndex2 = nextVertexIndex(vertexIndex1, nVertices, clockwise);
while (vertexIndex2 && areCoincidentPoints(polygon.vertexAt(vertexIndex1), polygon.vertexAt(vertexIndex2)))
vertexIndex2 = nextVertexIndex(vertexIndex2, nVertices, clockwise);
while (vertexIndex2) {
unsigned vertexIndex3 = nextVertexIndex(vertexIndex2, nVertices, clockwise);
if (!areCollinearPoints(polygon.vertexAt(vertexIndex1), polygon.vertexAt(vertexIndex2), polygon.vertexAt(vertexIndex3)))
break;
vertexIndex2 = vertexIndex3;
}
return vertexIndex2;
}
FloatPolygon::FloatPolygon(Vector<FloatPoint>&& vertices)
: m_vertices(WTFMove(vertices))
, m_empty(m_vertices.size() < 3)
, m_edges(m_vertices.size())
{
unsigned nVertices = numberOfVertices();
if (nVertices)
m_boundingBox.setLocation(vertexAt(0));
if (m_empty)
return;
unsigned minVertexIndex = 0;
for (unsigned i = 1; i < nVertices; ++i) {
const FloatPoint& vertex = vertexAt(i);
if (vertex.y() < vertexAt(minVertexIndex).y() || (vertex.y() == vertexAt(minVertexIndex).y() && vertex.x() < vertexAt(minVertexIndex).x()))
minVertexIndex = i;
}
FloatPoint nextVertex = vertexAt((minVertexIndex + 1) % nVertices);
FloatPoint prevVertex = vertexAt((minVertexIndex + nVertices - 1) % nVertices);
bool clockwise = FloatPolygonInternal::determinant(vertexAt(minVertexIndex) - prevVertex, nextVertex - prevVertex) > 0;
unsigned edgeIndex = 0;
unsigned vertexIndex1 = 0;
do {
m_boundingBox.extend(vertexAt(vertexIndex1));
unsigned vertexIndex2 = findNextEdgeVertexIndex(*this, vertexIndex1, clockwise);
m_edges[edgeIndex].m_polygon = this;
m_edges[edgeIndex].m_vertexIndex1 = vertexIndex1;
m_edges[edgeIndex].m_vertexIndex2 = vertexIndex2;
m_edges[edgeIndex].m_edgeIndex = edgeIndex;
++edgeIndex;
vertexIndex1 = vertexIndex2;
} while (vertexIndex1);
if (edgeIndex > 3) {
const FloatPolygonEdge& firstEdge = m_edges[0];
const FloatPolygonEdge& lastEdge = m_edges[edgeIndex - 1];
if (areCollinearPoints(lastEdge.vertex1(), lastEdge.vertex2(), firstEdge.vertex2())) {
m_edges[0].m_vertexIndex1 = lastEdge.m_vertexIndex1;
edgeIndex--;
}
}
m_edges.shrink(edgeIndex);
m_empty = m_edges.size() < 3;
if (m_empty)
return;
for (auto& edge : m_edges)
m_edgeTree.add({ edge.minY(), edge.maxY(), &edge });
}
Vector<std::reference_wrapper<const FloatPolygonEdge>> FloatPolygon::overlappingEdges(float minY, float maxY) const
{
auto overlappingEdgeIntervals = m_edgeTree.allOverlaps({ minY, maxY });
return overlappingEdgeIntervals.map([](auto& interval) -> std::reference_wrapper<const FloatPolygonEdge> {
return *interval.data();
});
}
bool VertexPair::intersection(const VertexPair& other, FloatPoint& point) const
{
// See: http://paulbourke.net/geometry/pointlineplane/, "Intersection point of two lines in 2 dimensions"
const FloatSize& thisDelta = vertex2() - vertex1();
const FloatSize& otherDelta = other.vertex2() - other.vertex1();
float denominator = FloatPolygonInternal::determinant(thisDelta, otherDelta);
if (!denominator)
return false;
// The two line segments: "this" vertex1,vertex2 and "other" vertex1,vertex2, have been defined
// in parametric form. Each point on the line segment is: vertex1 + u * (vertex2 - vertex1),
// when 0 <= u <= 1. We're computing the values of u for each line at their intersection point.
const FloatSize& vertex1Delta = vertex1() - other.vertex1();
float uThisLine = FloatPolygonInternal::determinant(otherDelta, vertex1Delta) / denominator;
float uOtherLine = FloatPolygonInternal::determinant(thisDelta, vertex1Delta) / denominator;
if (uThisLine < 0 || uOtherLine < 0 || uThisLine > 1 || uOtherLine > 1)
return false;
point = vertex1() + uThisLine * thisDelta;
return true;
}
#ifndef NDEBUG
TextStream& operator<<(TextStream& stream, const FloatPolygonEdge& edge)
{
return stream << &edge << " (" << edge.vertex1().x() << ',' << edge.vertex1().y() << ' ' << edge.vertex2().x() << ',' << edge.vertex2().y() << ')';
}
#endif
} // namespace WebCore
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