部分Android或IOS手机拍照后照片被旋转的问题

   class ImageNormal
    {

        public void NormalImageDegree(string imagePath)
        {
            var bitmap = (Bitmap)Bitmap.FromFile(imagePath);
            var exif = bitmap.GetExif();
            if (exif.Orientation == ExifNET.Models.Types.Orientation.Normal) return;
            Bitmap newBitmap = null;
            switch (exif.Orientation)
            {
                case ExifNET.Models.Types.Orientation.Rotate90:
                    newBitmap = rotateImage(bitmap, -90);
                    break;
                case ExifNET.Models.Types.Orientation.Rotate270:
                    newBitmap = rotateImage(bitmap, -270);
                    break;
                case ExifNET.Models.Types.Orientation.Rotate180:
                    newBitmap = rotateImage(bitmap, -180);
                    break;
                default:
                    break;
            }
            bitmap.Dispose();
            if (newBitmap != null)
            {
                newBitmap.Save(imagePath, System.Drawing.Imaging.ImageFormat.Jpeg);
                newBitmap.Dispose();
            }
        }
        private Bitmap rotateImage(Bitmap 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
            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;
        }

    }