使用C#进行图片转换格式,缩放,自动旋转,保留exif（转载）

这几天心血来潮做了一个批量图片缩放,转换格式,并且可以根据exif的信息旋转图片,校正exif信息后保存的小程序.根据配置文件 指定需要的功能.

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using System; using System.IO; using System.Drawing.Imaging; using System.Drawing; using System.Drawing.Drawing2D; using System.Runtime.InteropServices; using System.Text;   namespace PhotoUtil {     class Program     {         [DllImport("kernel32")]         private static extern long GetPrivateProfileString(string section, string key,             string def, StringBuilder retVal, int size, string filePath);         private const String configFile = "Config.ini";           public static void Main(string[] args)         {             DirectoryInfo workingDir = new DirectoryInfo(ReadConfig("General", "WorkingDir",Environment.CurrentDirectory));             if (!workingDir.Exists)             {                 workingDir = new DirectoryInfo(Environment.CurrentDirectory);             }             int quality=int.Parse(ReadConfig("General", "Quality", "85"));             bool needResize = Boolean.Parse(ReadConfig("ResizeImage", "Enable", "false"));             int newWidth = int.Parse(ReadConfig("ResizeImage", "NewWidth", "800"));             int newHeight = int.Parse(ReadConfig("ResizeImage", "NewHeight", "600"));             bool padding = Boolean.Parse(ReadConfig("ResizeImage", "Padding", "false"));             bool needRotate = Boolean.Parse(ReadConfig("RotateImage", "Enable", "true"));             FileInfo[] files = workingDir.GetFiles();             DirectoryInfo output = workingDir.CreateSubdirectory(DateTime.Now.ToString("yyyyMMdd") + "转换\r             foreach (FileInfo i in files)             {                 String type = i.Extension.ToLower();                 if (type.Contains("jpg") || type.Contains("jpeg") || (type.Contains("png")) || type.Contains("tif") || type.Contains("bmp"))                 {                     Image img = Image.FromFile(i.FullName);                     if (needResize)                     {                         Console.WriteLine("Resizing " + i.FullName);                         ResizeImage(ref img, newWidth, newHeight, padding);                     }                     if (needRotate)                     {                         Console.WriteLine("Rotating " + i.FullName);                         RotateImage(img);                     }                     SaveAs(img, output.FullName+"\\\\"+i.Name, quality);                 }             }             Console.ReadLine();         }           private static void SaveAs(Image img, string dest, long quality)         {             if (quality > 100 || quality < 1)             {                 quality = 85;             }             EncoderParameters para = new EncoderParameters();             para.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);             String extension = new FileInfo(dest).Extension;             ImageCodecInfo info = GetImageCodecInfoByExtension(extension);             if (info != null)             {                 img.Save(dest, info, para);             }             else             {                 throw new Exception("Unrecognized  format \\"" + extension + "\\"!\r             }         }           private static void ResizeImage(ref Image image, int expectDestWidth, int expectDestHeight,bool padding)         {             PropertyItem[] exif = image.PropertyItems;             int targetWidth = 0;             int targetHeight = 0;             double srcHWRate = (double)image.Width / (double)image.Height;             double expectHWRate = (double)expectDestWidth / (double)expectDestHeight;             if (srcHWRate > expectHWRate)             {                 targetWidth = expectDestWidth;                 targetHeight = System.Convert.ToInt32(Math.Round(expectDestWidth / srcHWRate, 0));             }             else             {                 targetHeight = expectDestHeight;                 targetWidth = System.Convert.ToInt32(Math.Round(expectDestHeight * srcHWRate, 0));             }               Image bitmap = null;             if (!padding)             {                 bitmap = new Bitmap(targetWidth, targetHeight);             }             else             {                 bitmap = new Bitmap(expectDestWidth, expectDestHeight);             }             Graphics g = Graphics.FromImage(bitmap);             g.CompositingQuality = CompositingQuality.HighQuality;             g.InterpolationMode = InterpolationMode.HighQualityBicubic;             g.SmoothingMode = SmoothingMode.HighQuality;             g.DrawImage(image, new Rectangle(0, 0, bitmap.Width, bitmap.Height), new Rectangle(0, 0, image.Width, image.Height), GraphicsUnit.Pixel);             foreach (PropertyItem i in exif)             {                 if (i.Id == 40962)                 {                     i.Value = BitConverter.GetBytes(targetWidth);                 }                 else if (i.Id == 40963)                 {                     i.Value = BitConverter.GetBytes(targetHeight);                 }                 bitmap.SetPropertyItem(i);             }             g.Dispose();             image.Dispose();             image = bitmap;         }           private static string ReadConfig(String Section, String Key, String defaultValue)         {             if (File.Exists(configFile))             {                 StringBuilder temp = new StringBuilder(1024);                 GetPrivateProfileString(Section, Key, String.Empty, temp, 1024, new FileInfo(configFile).FullName);                 if (!String.IsNullOrEmpty(temp.ToString()))                 {                     return temp.ToString();                 }                 else                 {                     return defaultValue;                 }             }             else             {                 return defaultValue;             }         }           public static void RotateImage(Image img)         {             PropertyItem[] exif = img.PropertyItems;             byte orientation = 0;             foreach (PropertyItem i in exif)             {                 if (i.Id == 274)                 {                     orientation = i.Value[0];                     i.Value[0] = 1;                     img.SetPropertyItem(i);                 }             }               switch (orientation)             {                 case 2:                     img.RotateFlip(RotateFlipType.RotateNoneFlipX);                     break;                 case 3:                     img.RotateFlip(RotateFlipType.Rotate180FlipNone);                     break;                 case 4:                     img.RotateFlip(RotateFlipType.RotateNoneFlipY);                     break;                 case 5:                     img.RotateFlip(RotateFlipType.Rotate90FlipX);                     break;                 case 6:                     img.RotateFlip(RotateFlipType.Rotate90FlipNone);                     break;                 case 7:                     img.RotateFlip(RotateFlipType.Rotate270FlipX);                     break;                 case 8:                     img.RotateFlip(RotateFlipType.Rotate270FlipNone);                     break;                 default:                     break;             }             foreach (PropertyItem i in exif)             {                 if (i.Id == 40962)                 {                     i.Value = BitConverter.GetBytes(img.Width);                 }                 else if (i.Id == 40963)                 {                     i.Value = BitConverter.GetBytes(img.Height);                 }             }         }           private static ImageCodecInfo GetImageCodecInfoByExtension(String extension)         {             ImageCodecInfo[] list = ImageCodecInfo.GetImageEncoders();             foreach(ImageCodecInfo i in list)             {                 if (i.FilenameExtension.ToLower().Contains(extension.ToLower()))                 {                     return i;                 }             }             return null;         }     } }

配置文件名称:Config.ini,放在和程序同目录下,格式如下:
[General]
#工作目录
WorkingDir=.
#输出质量，1-100范围内的整数
Quality=80

[ResizeImage]
#是否启用
Enable=true
#新的宽值和高值
NewWidth=1024
NewHeight=768
#是否对超出原来比例的部分进行填充
Padding=false

#是否使用Exif中的旋转信息对图片进行旋转
[RotateImage]
Enable=true

1.保留exif信息的技巧是获取原始的Image.PropertyItems,对新图片添加即可.
2.关于Exif Orientation标志的定义 http://sylvana.net/jpegcrop/exif_orientation.html
3.变更jpeg输出质量的方法:
EncoderParameters para = new EncoderParameters();
para.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);
//这里的quality是从1-100的long值,一开始想当然的以为1-100的值就用了byte,结果出错了.
最后调用Image.Save(String, ImageCodecInfo, EncoderParameters)来进行输出.
4.进行缩放/旋转后需要调整原始的exif信息,id查文档可知.列出一些
id=40962,width
id=40963,height
id=274,orientation type
对PropertyItem信息设置完了别忘了Image.SetPropertyItem(PropertyItem)添加到image中,我出一个很 傻的bug,就是在修改了orientation type=1之后没有SetPropertyItem,于是导致图片实际被旋转至正确角度了,但是用ACDSee打开后可以看到exif的旋转信息依旧是 原来的值.