基于C#的两种图片旋转方法

   

    /// 

        /// 根据角度旋转图标
        /// 
        /// 
        public Image RotateImg(Image img, float angle)
        {
            //通过Png图片设置图片透明，修改旋转图片变黑问题。
            int width = img.Width;
            int height = img.Height;                    
            //角度
            Matrix mtrx = new Matrix();           
            mtrx.RotateAt(angle, new PointF((width / 2), (height / 2)), MatrixOrder.Append);
            //得到旋转后的矩形
            GraphicsPath path = new GraphicsPath();
            path.AddRectangle(new RectangleF(0f, 0f, width, height));
            RectangleF rct = path.GetBounds(mtrx);
            //生成目标位图
            Bitmap devImage = new Bitmap((int)(rct.Width), (int)(rct.Height));
            Graphics g = Graphics.FromImage(devImage);
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Bilinear;
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;           
            //计算偏移量
            Point Offset = new Point((int)(rct.Width - width) / 2, (int)(rct.Height - height) / 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, (int)width, (int)height);
            Point center = new Point((int)(rect.X + rect.Width / 2), (int)(rect.Y + rect.Height / 2));            
            g.TranslateTransform(center.X, center.Y);
            g.RotateTransform(angle);
            //恢复图像在水平和垂直方向的平移
            g.TranslateTransform(-center.X, -center.Y);
            g.DrawImage(img, rect);
            //重至绘图的所有变换
            g.ResetTransform();
            g.Save();
            g.Dispose();
            path.Dispose();
            return devImage;
        }
        /// 

        /// 第二种方法
        /// 
        /// 
        /// 
        /// 
        public Image RotateImg2(Image b, float 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
            Image 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;
        }