关于图片的旋转

#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 Bitmap Rotate(Bitmap 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();

            //dsImage.Save("yuancd.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);

            return dsImage;

        }

        #endregion 图片旋转函数