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using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
namespace MonoGame.Extended.Shapes
{
public class Polygon : IEquatable<Polygon>
{
public Polygon(IEnumerable<Vector2> vertices)
{
_localVertices = vertices.ToArray();
_transformedVertices = _localVertices;
_offset = Vector2.Zero;
_rotation = 0;
_scale = Vector2.One;
_isDirty = false;
}
private readonly Vector2[] _localVertices;
private Vector2[] _transformedVertices;
private Vector2 _offset;
private float _rotation;
private Vector2 _scale;
private bool _isDirty;
public Vector2[] Vertices
{
get
{
if (_isDirty)
{
_transformedVertices = GetTransformedVertices();
_isDirty = false;
}
return _transformedVertices;
}
}
public float Left
{
get { return Vertices.Min(v => v.X); }
}
public float Right
{
get { return Vertices.Max(v => v.X); }
}
public float Top
{
get { return Vertices.Min(v => v.Y); }
}
public float Bottom
{
get { return Vertices.Max(v => v.Y); }
}
public void Offset(Vector2 amount)
{
_offset += amount;
_isDirty = true;
}
public void Rotate(float amount)
{
_rotation += amount;
_isDirty = true;
}
public void Scale(Vector2 amount)
{
_scale += amount;
_isDirty = true;
}
private Vector2[] GetTransformedVertices()
{
var newVertices = new Vector2[_localVertices.Length];
var isScaled = _scale != Vector2.One;
for (var i = 0; i < _localVertices.Length; i++)
{
var p = _localVertices[i];
if (isScaled)
p *= _scale;
// ReSharper disable once CompareOfFloatsByEqualityOperator
if (_rotation != 0)
{
var cos = (float) Math.Cos(_rotation);
var sin = (float) Math.Sin(_rotation);
p = new Vector2(cos*p.X - sin*p.Y, sin*p.X + cos*p.Y);
}
newVertices[i] = p + _offset;
}
return newVertices;
}
public Polygon TransformedCopy(Vector2 offset, float rotation, Vector2 scale)
{
var polygon = new Polygon(_localVertices);
polygon.Offset(offset);
polygon.Rotate(rotation);
polygon.Scale(scale - Vector2.One);
return new Polygon(polygon.Vertices);
}
public RectangleF BoundingRectangle
{
get
{
var minX = Left;
var minY = Top;
var maxX = Right;
var maxY = Bottom;
return new RectangleF(minX, minY, maxX - minX, maxY - minY);
}
}
public bool Contains(Vector2 point)
{
return Contains(point.X, point.Y);
}
public bool Contains(float x, float y)
{
var intersects = 0;
var vertices = Vertices;
for (var i = 0; i < vertices.Length; i++)
{
var x1 = vertices[i].X;
var y1 = vertices[i].Y;
var x2 = vertices[(i + 1)%vertices.Length].X;
var y2 = vertices[(i + 1)%vertices.Length].Y;
if ((((y1 <= y) && (y < y2)) || ((y2 <= y) && (y < y1))) && (x < (x2 - x1)/(y2 - y1)*(y - y1) + x1))
intersects++;
}
return (intersects & 1) == 1;
}
public static bool operator ==(Polygon a, Polygon b)
{
return a.Equals(b);
}
public static bool operator !=(Polygon a, Polygon b)
{
return !(a == b);
}
public override bool Equals(object obj)
{
if (ReferenceEquals(null, obj)) return false;
return obj is Polygon && Equals((Polygon) obj);
}
public bool Equals(Polygon other)
{
return Vertices.SequenceEqual(other.Vertices);
}
public override int GetHashCode()
{
unchecked
{
return Vertices.Aggregate(27, (current, v) => current + 13*current + v.GetHashCode());
}
}
}
}
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