图片旋转方法

图片旋转方法：

#region 图片旋转函数  
  
  
   /// <summary>  
  
   /// 以逆时针为方向对图像进行旋转  
  
   /// </summary>  
  
   /// <param name="b">位图流</param>  
  
   /// <param name="angle">旋转角度[0,360](前台给的)</param>  
  
   /// <returns></returns>  
  
   public Image RotateImg(Image b, int angle)  
  
   {  
  
   angle = angle % 360;  
  
  
   //弧度转换  
  
   double radian = angle * Math.PI / 180.0;  
  
   double cos = Math.Cos(radian);  
  
   double sin = Math.Sin(radian);  
  
  
   //原图的宽和高  
  
   int w = b.Width;  
  
   int h = b.Height;  
  
   int W = (int)(Math.Max(Math.Abs(w * cos - h * sin), Math.Abs(w * cos + h * sin)));  
  
   int H = (int)(Math.Max(Math.Abs(w * sin - h * cos), Math.Abs(w * sin + h * cos)));  
  
  
   //目标位图  
  
   Bitmap dsImage = new Bitmap(W, H);  
  
   System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(dsImage);  
  
   g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Bilinear;  
  
   g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;  
  
  
   //计算偏移量  
  
   Point Offset = new Point((W - w) / 2, (H - h) / 2);  
  
  
   //构造图像显示区域：让图像的中心与窗口的中心点一致  
  
   Rectangle rect = new Rectangle(Offset.X, Offset.Y, w, h);  
  
   Point center = new Point(rect.X + rect.Width / 2, rect.Y + rect.Height / 2);  
  
  
   g.TranslateTransform(center.X, center.Y);  
  
   g.RotateTransform(360 - angle);  
  
  
   //恢复图像在水平和垂直方向的平移  
  
   g.TranslateTransform(-center.X, -center.Y);  
  
   g.DrawImage(b, rect);  
  
  
   //重至绘图的所有变换  
  
   g.ResetTransform();  
  
  
   g.Save();  
  
   g.Dispose();  
  
   //保存旋转后的图片  
  
   b.Dispose();  
  
   dsImage.Save("FocusPoint.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);  
  
   return dsImage;  
  
   }