C#画圆的问题

Question

实现的效果是2步完成画圆~~第一个click确定圆心~第二个click确定半径~在确定半径的时候要图的整个样子要展现出来~~这样的画圆函数应该怎么写啊~？麻烦师兄些指点啊~~在线等~~

Answer 1

.net内部有自带的画圆函数，
按照你的描述，首先确定一个点，然后再确定半径，调用
Graphics.DrawEllipse方法你需要一个矩形来确定一个圆
实际上就是计算该矩形所在的位置以及边长的问题了，需要注意的是
矩形的位置是左上角确定的而圆心是位于矩形的中心

Answer 2

    private void button1_Click(object sender, EventArgs e)
        {            Graphics _Graphics = Graphics.FromHwnd(pictureBox1.Handle);            _Graphics.DrawEllipse(new Pen(Brushes.Yellow, 2), GetEllopse(new Point(50, 50), 10));
            _Graphics.Dispose();        }
        /// <summary>
        /// 根据圆心和半径获取图形坐标
        /// </summary>
        /// <param name="p_CenterPoint">圆心</param>
        /// <param name="p_Radius">半径</param>
        /// <returns>坐标</returns>
        public Rectangle GetEllopse(Point p_CenterPoint, int p_Radius)
        {
            int _X = p_CenterPoint.X - p_Radius;
            int _Y = p_CenterPoint.Y - p_Radius;
            return new Rectangle(_X, _Y, p_Radius * 2, p_Radius * 2);
        }

Answer 3

你需要的是在MouseMove事件中画圆，等会给你个详细代码，我先试下，以前做过。

Answer 4

你在窗体上加个pictureBox1
给pictureBox1加3个事件方法 MouseMove  MouseUp MouseDown
   /// <summary>
        /// 根据圆心和半径获取图形坐标
        /// </summary>
        /// <param name="p_CenterPoint">圆心</param>
        /// <param name="p_Radius">半径</param>
        /// <returns>坐标</returns>
        public Rectangle GetEllopse(Point p_CenterPoint, int p_Radius)
        {
            int _X = p_CenterPoint.X - p_Radius;
            int _Y = p_CenterPoint.Y - p_Radius;
            return new Rectangle(_X, _Y, p_Radius * 2, p_Radius * 2);
        }        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {            if (m_Panit)
            {
                Graphics _Graphics = pictureBox1.CreateGraphics();
                _Graphics.Clear(pictureBox1.BackColor);
                int _RadiusW = m_Point.X - e.X;
                int _RadiusH = m_Point.Y - e.Y;                _RadiusH = Math.Abs(_RadiusH);
                _RadiusW = Math.Abs(_RadiusW);
                if (_RadiusW > _RadiusH) _RadiusH = _RadiusW;
                Rectangle _EllopseRectangle = GetEllopse(m_Point, _RadiusH);                _Graphics.DrawEllipse(new Pen(Brushes.Yellow, 2), _EllopseRectangle);
                
                _Graphics.Dispose();
            }
        }
        /// <summary>
        /// 绘制标示
        /// </summary>
        private bool m_Panit = false;
        /// <summary>
        /// 开始坐标
        /// </summary>
        private Point m_Point = new Point(0, 0);        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            m_Panit = true;
            m_Point.X = e.X;
            m_Point.Y = e.Y;
        }
   private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            m_Panit = false;
           
        }
 
        

Answer 5

pictureBox1 
是添加的图片~？

Answer 6

public int CursorX,CursorY,r;
public Image theimage；
public Graphics ig,g;private void Form1_Load(object sender, System.EventArgs e)
{
        theimage=new Bitmap(this.pictureBox1.ClientRectangle.Width,this.pictureBox1.ClientRectangle.Height);
        ig=Graphics.FromImage(theimage);
ig.InterpolationMode=System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
g=this.pictureBox1.CreateGraphics();
g.InterpolationMode=System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
}private void pictureBox1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
if(CursorMod==0)
        {
CursorMod=1;
CursorX=e.X;
CursorY=e.Y;
}
else
{
CursorMod=0;
ig.DrawEllipse(new Pen(Color.Green,1),CursorX-r,CursorY-r,2*r,2*r);
                pictureBox1.Image=theimage;
}
}private void pictureBox1_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
{
        if(CursorMod==1)
{
this.pictureBox1.Refresh();
r=Convert.ToInt32(Math.Sqrt(Math.Abs(e.X-CursorX)*Math.Abs(e.X-CursorX)+Math.Abs(e.Y-CursorY)*Math.Abs(e.Y-CursorY)));
g.DrawEllipse(new Pen(Color.Green,1),CursorX-r,CursorY-r,2*r,2*r);
}
        else//CursorMod==0
{
this.pictureBox1.Refresh();
        }
}