C# 画国标五星红旗

 public interface INationFlag
2 {
3     float WidthProportion { get; }
4     float HeightProportion { get; }
5     SizeF Size { get; set; }
6 
7     void AdjustFlagSizeF(int width);
8     Image GetFlagImage();
9 }

  1 class ChinaFlag : INationFlag
  2 {
  3     #region -  INationFlag Members  -
  4 
  5     public float WidthProportion { get { return 3F; } }
  6     public float HeightProportion { get { return 2F; } }
  7 
  8     SizeF size = SizeF.Empty;
  9 
 10     public SizeF Size
 11     {
 12         get { return size; }
 13         set { if (size != value) size = value; }
 14     }
 15 
 16     public void AdjustFlagSizeF(int w)
 17     {
 18         int width = w + w % (int)WidthProportion;
 19         int height = (int)(HeightProportion * width / WidthProportion);
 20 
 21         Size = new SizeF(width, height);
 22     }
 23 
 24     public Image GetFlagImage()
 25     {
 26         Bitmap flag = new Bitmap((int)size.Width, (int)size.Height);
 27         float piece = size.Width / 30;
 28 
 29         int bigStarRadius = (int)(piece * 3);
 30         int smlStarRadius = (int)piece;
 31 
 32         using (Graphics g = Graphics.FromImage(flag))
 33         {
 34             g.SmoothingMode = SmoothingMode.AntiAlias;
 35             g.FillRectangle(Brushes.Red, 0, 0, size.Width, size.Height);
 36 
 37             g.DrawImage(GetStarImage(bigStarRadius), piece * 2, piece * 2);
 38             g.DrawImage(GetStarImage(smlStarRadius, -(int)(Math.Atan(3.0 / 5.0) * 180.0 / Math.PI) - 18), piece * 9, piece);
 39             g.DrawImage(GetStarImage(smlStarRadius, -(int)(Math.Atan(1.0 / 7.0) * 180.0 / Math.PI) - 18), piece * 11, piece * 3);
 40             g.DrawImage(GetStarImage(smlStarRadius, 0), piece * 11, piece * 6);
 41             g.DrawImage(GetStarImage(smlStarRadius, (int)(Math.Atan(4.0 / 5.0) * 180.0 / Math.PI) - 18), piece * 9, piece * 8);
 42         }
 43 
 44         return flag;
 45     }
 46 
 47     #endregion
 48 
 49     #region -  Private Members  -
 50 
 51     public Image GetStarImage(int radius)
 52     {
 53         Bitmap bigStar = new Bitmap(radius * 2, radius * 2);
 54 
 55         using (Graphics g = Graphics.FromImage(bigStar))
 56         {
 57             g.SmoothingMode = SmoothingMode.AntiAlias;
 58             Point pc = new Point(radius, radius);
 59 
 60             PointF p0 = new PointF(pc.X, pc.Y - radius);
 61             PointF p1 = new PointF((float)(pc.X + radius * Math.Sin(72 * Math.PI / 180)), (float)(pc.Y - radius * Math.Cos(72 * Math.PI / 180)));
 62             PointF p2 = new PointF((float)(pc.X + radius * Math.Sin(36 * Math.PI / 180)), (float)(pc.Y + radius * Math.Cos(36 * Math.PI / 180)));
 63             PointF p3 = new PointF((float)(pc.X - radius * Math.Sin(36 * Math.PI / 180)), (float)(pc.Y + radius * Math.Cos(36 * Math.PI / 180)));
 64             PointF p4 = new PointF((float)(pc.X - radius * Math.Sin(72 * Math.PI / 180)), (float)(pc.Y - radius * Math.Cos(72 * Math.PI / 180)));
 65 
 66             using (GraphicsPath path = new GraphicsPath(FillMode.Winding))
 67             {
 68                 path.AddLine(p0, p2);
 69                 path.AddLine(p2, p4);
 70                 path.AddLine(p4, p1);
 71                 path.AddLine(p1, p3);
 72                 path.AddLine(p3, p0);
 73                 path.CloseFigure();
 74                 g.FillPath(Brushes.Yellow, path);
 75             }
 76         }
 77         return bigStar;
 78     }
 79 
 80     public Image GetStarImage(int radius, int angle)
 81     {
 82         return RotateImage(GetStarImage(radius), angle);
 83     }
 84     public Image RotateImage(Image b, int angle)
 85     {
 86         angle = angle % 360;
 87         // 弧度转换
 88          double radian = angle * Math.PI / 180.0;
 89         double cos = Math.Cos(radian);
 90         double sin = Math.Sin(radian);
 91         // 原图的宽和高
 92         int w = b.Width;
 93         int h = b.Height;
 94         int W = (int)(Math.Max(Math.Abs(w * cos - h * sin), Math.Abs(w * cos + h * sin)));
 95         int H = (int)(Math.Max(Math.Abs(w * sin - h * cos), Math.Abs(w * sin + h * cos)));
 96         // 目标位图
 97         Bitmap dsImage = new Bitmap(W, H);
 98         using (Graphics g = Graphics.FromImage(dsImage))
 99         {
100             g.InterpolationMode = InterpolationMode.Bilinear;
101             g.SmoothingMode = SmoothingMode.AntiAlias;
102             // 计算偏移量
103               Point Offset = new Point((W - w) / 2, (H - h) / 2);
104             // 构造图像显示区域：让图像的中心与窗口的中心点一致
105             Rectangle rect = new Rectangle(Offset.X, Offset.Y, w, h);
106             Point center = new Point(rect.X + rect.Width / 2, rect.Y + rect.Height / 2);
107             g.TranslateTransform(center.X, center.Y);
108             g.RotateTransform(angle - 360);
109             // 恢复图像在水平和垂直方向的平移
110             g.TranslateTransform(-center.X, -center.Y);
111             g.DrawImage(b, rect);
112             // 重至绘图的所有变换
113             g.ResetTransform();
114             g.Save();
115 
116         }
117         return dsImage.Clone(new Rectangle((W - w) / 2, (H - h) / 2, w, h), PixelFormat.DontCare);
118     }
119 
120     #endregion
121 
122     #region -  Constructor  -
123 
124     public ChinaFlag(int w)
125     {
126         AdjustFlagSizeF(w);
127     }
128 
129     #endregion
130 }
131 

 1 public partial class FrmMain : Form
 2 {
 3     public FrmMain()
 4     {
 5         InitializeComponent();
 6     }
 7     private void pbxCanvas_Paint(object sender, PaintEventArgs e)
 8     {
 9         INationFlag chinaFlag = new ChinaFlag(pbxCanvas.Width);
10         e.Graphics.DrawImage(chinaFlag.GetFlagImage(), 0, 0);
11     }
12     private void pbxCanvas_Resize(object sender, EventArgs e)
13     {
14         pbxCanvas.Invalidate();
15     }
16 }