不需要线性代数就可以进行形状的命中测试。您可以为形状创建GraphicsPath
,然后使用GraphicsPath.IsVisible
方法或GraphicsPath.IsOutlineVisible
方法执行命中测试。
示例
例如,您可以创建一个基础的IShape
接口,其中包含用于命中测试、绘制和移动的方法,然后在类中实现这些方法。还可以创建一个DrawingSurface
控件,它可以处理命中测试、绘制和移动IShape
对象。
在下面的示例中,我们创建了IShape
接口、Line
和Circle
类。还创建了一个DrawingSurface
控件。要测试示例,只需在Form
中放置一个DrawingSurface
控件并处理Load
事件,然后添加一些形状,运行应用程序并尝试移动形状即可。
IShape
此接口包含一些有用的方法,如果任何类实现它们,则可以用于绘制、命中测试和移动。在此示例结束时,您可以看到一个DrawingSurface
控件,它可以简单地与IShape
实现一起使用:
public interface IShape
{
GraphicsPath GetPath();
bool HitTest(Point p);
void Draw(Graphics g);
void Move(Point d);
}
线条
这里是一个实现了 IShape
接口的线条类。当你点击线条进行命中测试时,HitTest
返回 true。为了让你更简单地选择线条,我添加了两个点进行命中测试:
public class Line : IShape
{
public Line() { LineWidth = 2; LineColor = Color.Black; }
public int LineWidth { get; set; }
public Color LineColor { get; set; }
public Point Point1 { get; set; }
public Point Point2 { get; set; }
public GraphicsPath GetPath()
{
var path = new GraphicsPath();
path.AddLine(Point1, Point2);
return path;
}
public bool HitTest(Point p)
{
var result = false;
using (var path = GetPath())
using (var pen = new Pen(LineColor, LineWidth + 2))
result = path.IsOutlineVisible(p, pen);
return result;
}
public void Draw(Graphics g)
{
using (var path = GetPath())
using (var pen = new Pen(LineColor, LineWidth))
g.DrawPath(pen, path);
}
public void Move(Point d)
{
Point1 = new Point(Point1.X + d.X, Point1.Y + d.Y);
Point2 = new Point(Point2.X + d.X, Point2.Y + d.Y);
}
}
圆形
这里是一个实现了IShape
接口的圆形类。当进行点击测试时,如果你点击在圆形内部,HitTest
会返回True:
public class Circle : IShape
{
public Circle() { FillColor = Color.Black; }
public Color FillColor { get; set; }
public Point Center { get; set; }
public int Radious { get; set; }
public GraphicsPath GetPath()
{
var path = new GraphicsPath();
var p = Center;
p.Offset(-Radious, -Radious);
path.AddEllipse(p.X, p.Y, 2 * Radious, 2 * Radious);
return path;
}
public bool HitTest(Point p)
{
var result = false;
using (var path = GetPath())
result = path.IsVisible(p);
return result;
}
public void Draw(Graphics g)
{
using (var path = GetPath())
using (var brush = new SolidBrush(FillColor))
g.FillPath(brush, path);
}
public void Move(Point d)
{
Center = new Point(Center.X + d.X, Center.Y + d.Y);
}
}
DrawingSurface
该控件可以绘制一系列形状,并且能够在MouseDown
事件中执行命中测试,如果拖动则可移动形状。您应该将一些形状如Line
或Circle
添加到控件的Shapes
集合中。
public class DrawingSurface : Control
{
public List<IShape> Shapes { get; private set; }
IShape selectedShape;
bool moving;
Point previousPoint = Point.Empty;
public DrawingSurface() { DoubleBuffered = true; Shapes = new List<IShape>(); }
protected override void OnMouseDown(MouseEventArgs e)
{
for (var i = Shapes.Count - 1; i >= 0; i--)
if (Shapes[i].HitTest(e.Location)) { selectedShape = Shapes[i]; break; }
if (selectedShape != null) { moving = true; previousPoint = e.Location; }
base.OnMouseDown(e);
}
protected override void OnMouseMove(MouseEventArgs e)
{
if (moving) {
var d = new Point(e.X - previousPoint.X, e.Y - previousPoint.Y);
selectedShape.Move(d);
previousPoint = e.Location;
this.Invalidate();
}
base.OnMouseMove(e);
}
protected override void OnMouseUp(MouseEventArgs e)
{
if (moving) { selectedShape = null; moving = false; }
base.OnMouseUp(e);
}
protected override void OnPaint(PaintEventArgs e)
{
e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
foreach (var shape in Shapes)
shape.Draw(e.Graphics);
}
}
GraphicsPath.IsVisible
来检查一个点是否在路径中。 - Reza Aghaei