gdi绘制时钟的问题

Question

int sec_X = (int)(centerPoint.X + Math.Sin(6*Math.PI/180*s)*s_Len);求秒针顶点的X坐标 
谁能帮我解释一下啊 为什么用Sin啊 还有半径怎么没用啊 int sec_Y = (int)(centerPoint.Y - Math.Cos(6*Math.PI/180*s)*s_Len);
求秒针顶点Y坐标
为什么用的是centerPoint.Y -
而不用centerPoint.Y +  啊谢谢了

Answer 1

具体实现这个地址有：
http://www.cnblogs.com/hocylan/archive/2008/01/03/1024753.html（博客另外一篇文章有源码）完整代码如下：using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Drawing.Drawing2D;using System.Text;using System.Windows.Forms;namespace clock{    public partial class Form1 : Form    {        private Graphics g;        private Pen pen;        private FontFamily MyFamily;        private Font MyFont;        private int w;        private int h;        public Form1()        {            InitializeComponent();                  }        private void Form1_Load(object sender, EventArgs e)        {            timer_Second.Start(); //开启定时器            timer_Second.Interval = 1000; //间隔为毫秒，即秒        }        protected override void OnPaint(PaintEventArgs e)        {            base.OnPaint(e);            g = e.Graphics;            g.SmoothingMode = SmoothingMode.AntiAlias; //            g.SmoothingMode = SmoothingMode.HighQuality;//绘图模式默认为粗糙模式，将会出现锯齿！                      w = pictureBox1.Width;            h = pictureBox1.Height;            int x1 = pictureBox1.Location.X;            int y1 = pictureBox1.Location.Y;            /*------------------------------------------------------------------------------            计算：整点刻度个，每个刻度偏移角度为/12 = 30 度及为小时偏移角度                  分秒刻度为个，每个刻度偏移角度为 /60 = 6 度及为分、秒偏移角度            --------------------------------------------------------------------------------*/            g.FillEllipse(Brushes.Black, x1+2,y1+2, w - 4, h - 4); //外圆            MyFamily = new System.Drawing.FontFamily("Impact"); //字体            MyFont = new System.Drawing.Font(MyFamily, 20, FontStyle.Bold, GraphicsUnit.Pixel);            g.DrawString("HOCYLAN", MyFont, Brushes.Yellow, x1 + w-180, y1 + h -100);            MyFamily = new System.Drawing.FontFamily("Times New Roman");            MyFont = new System.Drawing.Font(MyFamily, 14, FontStyle.Bold, GraphicsUnit.Pixel);            pen = new Pen(Color.White, 2);            g.DrawEllipse(pen, x1+7, y1+7, w - 13, h - 13);// 内圆            g.TranslateTransform(x1+(w / 2),y1+(h / 2));//重新设置坐标原点            g.FillEllipse(Brushes.White, -5,-5, 10, 10);//绘制表盘中心            //g.TranslateTransform(w/2,h/2);            for (int x = 0; x < 60; x++) //小刻度            {                g.FillRectangle(Brushes.White, new Rectangle(-2, (System.Convert.ToInt16(h- 8) / 2 - 2) * (-1), 3, 10));                g.RotateTransform(6);//偏移角度            }            for (int i = 12; i > 0; i--) //大刻度            {                string myString = i.ToString();                //绘制整点刻度                g.FillRectangle(Brushes.White, new Rectangle(-3, (System.Convert.ToInt16(h - 8) / 2 - 2) * (-1), 6, 20));                //绘制数值                g.DrawString(myString, MyFont, Brushes.White, new PointF(myString.Length * (-6),( h - 8) / -2 + 26));                //顺时针旋转度                g.RotateTransform(-30);//偏移角度            }        }        private void pictureBox1_Paint(object sender, PaintEventArgs e)        {            g = e.Graphics;            //绘图模式默认为粗糙模式，将会出现锯齿！            g.SmoothingMode = SmoothingMode.AntiAlias;            g.SmoothingMode = SmoothingMode.HighQuality;            g.TranslateTransform(w / 2, h / 2);//重新设置坐标原点            //获得系统时间值            int second = DateTime.Now.Second;            int minute = DateTime.Now.Minute;            int hour = DateTime.Now.Hour;            /*------------------------------------------------------------------------------------            每秒偏移度，秒针偏移=当前秒*6            每分偏移读，分针偏移= 当前分*6+当前秒*（/60）            每小时偏移读，时针偏移= 当前时*30+当前分*（/60）+当前秒*（/60/60）            --------------------------------------------------------------------------------------*/            //绘秒针            pen = new Pen(Color.White, 1);            pen.EndCap = LineCap.ArrowAnchor;            g.RotateTransform(6 * second);            float y = (float)((-1) * (h / 2.75));            g.DrawLine(pen, new PointF(0, 0), new PointF((float)0, y));            ////绘分针            pen = new Pen(Color.White, 4);           // pen.EndCap = LineCap.ArrowAnchor;            g.RotateTransform(-6 * second); //恢复系统偏移量，再计算下次偏移            g.RotateTransform((float)(second*0.1+minute*6));            y = (float)((-1) * ((h-20) / 2.75));            g.DrawLine(pen, new PointF(0, 0), new PointF((float)0, y));            ////绘时针            pen = new Pen(Color.White, 6);           // pen.EndCap = LineCap.ArrowAnchor;            g.RotateTransform((float)(-second * 0.1 - minute * 6));//恢复系统偏移量，再计算下次偏移            g.RotateTransform((float)(second * 0.01 + minute * 0.1+hour*30));            y = (float)((-1) * ((h-35) / 2.75));            g.DrawLine(pen, new PointF(0, 0), new PointF((float)0, y));        }        private void timer1_Tick(object sender, EventArgs e)        {            pictureBox1.Invalidate();//只重新绘制pictureBox            }        }}

Answer 2

int sec_X = (int)(centerPoint.X + Math.Sin(6*Math.PI/180*s)*s_Len);
s，s_Len是什么？肯定与半径有关吧，秒针的终点在圆周上，其位置肯定与三角函数有关啊

Answer 3

int sec_Y = (int)(centerPoint.Y - Math.Cos(6*Math.PI/180*s)*s_Len);
加红的部分可以取负值，所以“-”也有可能是“+”，具体分析一下坐标系是怎么定义的