我有n个多边形，如下所示。
videoView.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
@Override
public void onPrepared(MediaPlayer mediaPlayer) {
mediaController.setAnchorView(videoView);
videoView.start();
}
});
请帮助我确定这些多边形中的三角形是什么
我试图确定如下所示的顶点。
<Polygon Points="544,245,544,175,568,175,568,175" Stroke="Black" StrokeThickness="1" />
<Polygon Points="2,223,96,223,96,153,96,153" Stroke="Black" StrokeThickness="1" />
<Polygon Points="350,315,350,333,306,333,306,395,306,395" Stroke="Black" StrokeThickness="1" />
<Polygon Points="164,53,160,53,160,51,160,55,160,55" Stroke="Black" StrokeThickness="1" />
<Polygon Points="264,63,264,58,264,68,264,63,267,63,267,60,267,66,267,63,270,63,270,58,270,68,270,68" Stroke="Black" StrokeThickness="1" />
<Polygon Points="8,63,444,63,444,168,444,168" Stroke="Black" StrokeThickness="1" />
<Polygon Points="212,169,212,93,285,93,285,63,285,63" Stroke="Black" StrokeThickness="1" />
<Polygon Points="26,93,127,93,127,148,29,148,29,148" Stroke="Black" StrokeThickness="1" />
<Polygon Points="152,116,152,132,212,132,212,132" Stroke="Black" StrokeThickness="1" />
<Polygon Points="121,316,121,333,70,333,70,366,70,366" Stroke="Black" StrokeThickness="1" />
<Polygon Points="464,395,488,395,488,284,527,284,527,284" Stroke="Black" StrokeThickness="1" />
<Polygon Points="168,63,168,67,180,59,180,67,168,59,168,59" Stroke="Black" StrokeThickness="1" />
<Polygon Points="173,62,173,56,165,56,165,51,175,51,175,61,175,61" Stroke="Black" StrokeThickness="1" />
<Polygon Points="3,285,121,285,121,316,211,316,211,304,211,304" Stroke="Black" StrokeThickness="1" />
但是上面的代码不适用于 Polygon polygon = new Polygon();
polygon.Points = new System.Windows.Media.PointCollection()
{
new Point(446,134),
new Point(442,134),
new Point(444,140),
new Point(444,140),
};
List<double> verticesPoints = new List<double>();
for (int i = 0; i < polygon.Points.Count - 1; i++)
{
var point1 = polygon.Points[i];
var point2 = polygon.Points[i + 1];
//calculate delta x and delta y between the two points
var deltaX = Math.Pow((point2.X - point1.X), 2);
var deltaY = Math.Pow((point2.Y - point1.Y), 2);
//pythagras theorem for distance
var distance = Math.Sqrt(deltaY + deltaX);
//distance is zero..then same point
if (distance != 0)
{
verticesPoints.Add(distance);
}
}
///Here is the code to calculate angle and consider the triangle
///three vertices then it might be triangle.
if (verticesPoints.Count == 3)
{
///use The Law of Cosines
///cos(C) = a2 + b2 − c2 /2ab
///cos(A) = b2 + c2 − a2 /bc
///cos(B) = c2 + a2 − b2 /ca
var a = ((Math.Pow(verticesPoints[1], 2)) + (Math.Pow(verticesPoints[2], 2)) - (Math.Pow(verticesPoints[0], 2)))
/ (2 * verticesPoints[1] * verticesPoints[2]);
var b = ((Math.Pow(verticesPoints[0], 2)) + (Math.Pow(verticesPoints[2], 2)) - (Math.Pow(verticesPoints[1], 2)))
/ (2 * verticesPoints[0] * verticesPoints[2]);
var c = ((Math.Pow(verticesPoints[0], 2)) + (Math.Pow(verticesPoints[1], 2)) - (Math.Pow(verticesPoints[2], 2)))
/ (2 * verticesPoints[0] * verticesPoints[1]);
///Inverse of cos
var radians1 = Math.Acos(a);
///Convert radian to degree
double degrees1 = (radians1 * 180.0) / Math.PI;
///Inverse of cos
var radians2 = Math.Acos(b);
//Convert radian to degree
double degrees2 = (radians2 * 180.0) / Math.PI;
///Inverse of cos
var radians3 = Math.Acos(c);
///Convert radian to degree
double degrees3 = (radians3 * 180.0) / Math.PI;
var totalDegrees = degrees1 + degrees2 + degrees3;
if (totalDegrees == 180)
{
// Consider triangle
}
}
，它只给出两个顶点，但是它是一个三角形，有些情况下得到3个顶点，但是totalDegrees不等于180
答案 0 :(得分：1)
此代码在此迭代遍历各个点并计算它们之间的梯度。如果两个连续点的梯度相同，则它们必须在同一条线上，因此noOfPoints不会增加，否则会增加。
第一个渐变存储在firstGradient中，以便检查连接最后一个点和第一个点的渐变是否与第一个点和第二个点之间的渐变相同。
Polygon polygon = new Polygon();
polygon.Points = new System.Windows.Media.PointCollection()
{
new Point(446,134),
new Point(442,134),
new Point(444,140),
new Point(444,140),
};
List<double> verticesPoints = new List<double>();
double? firstGradient = null;
double? gradient = null;
double? newGradient = null;
int noOfSides = 1;
for (int i = 0; i < polygon.Points.Count - 1; i++)
{
var point1 = polygon.Points[i];
var point2 = polygon.Points[i + 1];
if(point1 == point2) { continue;}
//calculate delta x and delta y between the two points
var deltaX = point2.X - point1.X;
var deltaY = point2.Y - point1.Y;
//calculate gradient
newGradient = (deltaY / deltaX);
if (i == 0)
{
firstGradient = newGradient;
}
if ((gradient != newGradient) && (i != polygon.Points.Count - 2))
{
noOfSides++;
}
else if (i == polygon.Points.Count - 2)
{
if ((gradient != newGradient) && (firstGradient != newGradient)) //This now checks the gradient between the last and first point.
{
point1 = polygon.Points[i+1];
point2 = polygon.Points[0];
if (point1 == point2) { continue; }
//calculate delta x and delta y between the two points
deltaX = point2.X - point1.X;
deltaY = point2.Y - point1.Y;
//calculate gradient
newGradient = (deltaY / deltaX);
if(newGradient != firstGradient)
{
noOfSides++;
}
}
gradient = newGradient;
}
答案 1 :(得分：0)
我已经使用“ AForge.NET”解决了上述问题
Polygon polygon = new Polygon();
polygon.Points = new PointCollection()
{
new Point(446,134),
new Point(442,134),
new Point(444,140),
new Point(444,140),
};
SimpleShapeChecker shapeChecker = new SimpleShapeChecker();
List<IntPoint> edgePoints = new List<IntPoint>();
List<IntPoint> corners;
for (int i = 0; i <= polygon.Points.Count - 1; i++)
{
edgePoints.Add(new IntPoint((int)polygon.Points[i].X, (int)polygon.Points[i].Y));
}
shapeChecker.MinAcceptableDistortion = 0.2f;
shapeChecker.LengthError = 0;
shapeChecker.AngleError = 5;
shapeChecker.RelativeDistortionLimit = 0;
if (shapeChecker.IsTriangle(edgePoints, out corners))
{
//shape is triangle
}
需要在名称空间下添加
using AForge;
using AForge.Math.Geometry;