C#实现根据图片的EXIF自动调整图片方向转

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一、什么是 EXIF

Exif是英文Exchangeable Image File(可交换图像文件)的缩写，最初由日本电子工业发展协会(JEIDA --Japan Electronic Industry Development Association) 制订，目前的最新版本是发表于2002年04月的2.21 版。国际标准化组织(ISO)正在制订的相机文件设计标准（DCF -- Design role for Camera File system）可能以Exif2.1为基础。

      所有的JPEG文件以字符串“0xFFD8”开头，并以字符串“0xFFD9”结束。文件头中有一系列“0xFF??”格式的字符串，称为“标识”，用来标记JPEG文件的信息段。“0xFFD8”表示图像信息开始，“0xFFD9”表示图像信息结束，这两个标识后面没有信息，而其它标识紧跟一些信息字符。　　0xFFE0 -- 0xFFEF之间的标识符称为“应用标记”，没有被常规JPEG文件利用，Exif正是利用这些信息串记录拍摄信息如快门速度、光圈值等，甚至可以包括全球定位信息。其中拍摄方向的ID为“0x0112”，有1至8共8种值。

二、EXIF Orientation

Orientation
The image orientation viewed in terms of rows and columns.
Tag = 274 (112.H)
Type = SHORT
Count = 1
Default = 1
1 = The 0th row is at the visual top of the image, and the 0th column is the visual left-hand side.
2 = The 0th row is at the visual top of the image, and the 0th column is the visual right-hand side.
3 = The 0th row is at the visual bottom of the image, and the 0th column is the visual right-hand side.
4 = The 0th row is at the visual bottom of the image, and the 0th column is the visual left-hand side.
5 = The 0th row is the visual left-hand side of the image, and the 0th column is the visual top.
6 = The 0th row is the visual right-hand side of the image, and the 0th column is the visual top.
7 = The 0th row is the visual right-hand side of the image, and the 0th column is the visual bottom.
8 = The 0th row is the visual left-hand side of the image, and the 0th column is the visual bottom.
Other = reserved
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一、使用C#旋转图片

        public static void rotating(Bitmap img,ref int width, ref int height, int orien)
        {
            int ow = width;
            switch (orien)
            {
                case 2:
                    img.RotateFlip(RotateFlipType.RotateNoneFlipX);//horizontal flip
                    break;
                case 3:
                    img.RotateFlip(RotateFlipType.Rotate180FlipNone);//right-top
                    break;
                case 4:
                    img.RotateFlip(RotateFlipType.RotateNoneFlipY);//vertical flip
                    break;
                case 5:
                    img.RotateFlip(RotateFlipType.Rotate90FlipX);
                    break;
                case 6:
                    img.RotateFlip(RotateFlipType.Rotate90FlipNone);//right-top
                    width = height;
                    height = ow;
                    break;
                case 7:
                    img.RotateFlip(RotateFlipType.Rotate270FlipX);
                    break;
                case 8:
                    img.RotateFlip(RotateFlipType.Rotate270FlipNone);//left-bottom
                    width = height;
                    height = ow;
                    break;
                default:
                    break;
            }
        }