保存到磁盘之前压缩和解压缩文件

Question

在我的应用程序中，我有一个Web服务从FormData（客户端）获取一个文件，并且我想在保存到磁盘之前压缩该文件（不使用额外的文件夹）。

我从这里读了很多答案，但我感到困惑，我将在后面的代码中使用哪种方法来实现更好的压缩。并且我还想在访问时解压该文件。

当前在代码后面我使用波纹管代码直接保存文件。

var httpPostedFile = HttpContext.Current.Request.Files["UploadedImage"]; 
// Get the complete file path 
var fileSavePath = Path.Combine(HttpContext.Current.Server.MapPath("~/Download/"), httpPostedFile.FileName); 
// Save the uploaded file to "UploadedFiles" folder 
httpPostedFile.SaveAs(fileSavePath); 

Answer 1

我们可以通过不同的方式做到这一点，

的最佳途径之一就是将所有图像转换成JPEG格式，因为它会提供更好的清晰度与尺寸更小，在这方面我们并不需要改变该特定图像的任何高度或宽度

方法1：所有图像转换成JPEG（不需要附加的压缩）

private static void VaryQualityLevel(Image imgToResize,string imageName) 
     { 
     // Get a bitmap. 
     Bitmap bmp1 = new Bitmap(imgToResize); 
     ImageCodecInfo jgpEncoder = GetEncoder(ImageFormat.Jpeg); 

     // Create an Encoder object based on the GUID 
     // for the Quality parameter category. 
     System.Drawing.Imaging.Encoder myEncoder = 
      System.Drawing.Imaging.Encoder.Quality; 

     // Create an EncoderParameters object. 
     // An EncoderParameters object has an array of EncoderParameter 
     // objects. In this case, there is only one 
     // EncoderParameter object in the array. 
     EncoderParameters myEncoderParameters = new EncoderParameters(1); 

     EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, 
      50L); 
     myEncoderParameters.Param[0] = myEncoderParameter; 

     var fileSavePath = Path.Combine(HttpContext.Current.Server.MapPath("~/Download/"), imageName+".jpeg"); 
     bmp1.Save(fileSavePath, jgpEncoder, 
      myEncoderParameters); 

     //myEncoderParameter = new EncoderParameter(myEncoder, 100L); 
     //myEncoderParameters.Param[0] = myEncoderParameter; 
     //fileSavePath = Path.Combine(HttpContext.Current.Server.MapPath("~/Download/"), "TestPhotoQuality100.jpeg"); 
     //bmp1.Save(fileSavePath, jgpEncoder, 
     // myEncoderParameters); 

     // Save the bitmap as a JPG file with 75 quality level compression. 
     myEncoderParameter = new EncoderParameter(myEncoder, 75L); 
     //myEncoderParameters.Param[0] = myEncoderParameter; 
     //fileSavePath = Path.Combine(HttpContext.Current.Server.MapPath("~/Download/"), "TestPhotoQuality75.jpeg"); 
     //bmp1.Save(fileSavePath, jgpEncoder, 
     // myEncoderParameters); 

    } 

    private static ImageCodecInfo GetEncoder(ImageFormat format) 
    { 

     ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders(); 

     foreach (ImageCodecInfo codec in codecs) 
     { 
      if (codec.FormatID == format.Guid) 
      { 
       return codec; 
      } 
     } 
     return null; 
     } 

方法2：通过改变高度和WIDT图像的H（无JPEG转换）

CommonConstant.CS

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 

namespace EmptyDemo.compression 
{ 
#region[Directive] 
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
#endregion[Directive] 

/// <summary> 
/// This class is used to get the constants 
/// </summary> 
public class CommonConstant 
{ 
    public const string JPEG = ".jpeg"; 
    public const string PNG = ".png"; 
    public const string JPG = ".jpg"; 
    public const string BTM = ".btm"; 
} 
} 

ImageCompress.CS

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 

namespace EmptyDemo.compression 
{ 
#region[Directive] 
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Drawing; 
using System.Drawing.Imaging; 
using System.IO; 
#endregion[Directive] 

/// <summary> 
/// This class is used to compress the image to 
/// provided size 
/// </summary> 
public class ImageCompress 
{ 
    #region[PrivateData] 
    private static volatile ImageCompress imageCompress; 
    private Bitmap bitmap; 
    private int width; 
    private int height; 
    private Image img; 
    #endregion[Privatedata] 

    #region[Constructor] 
    /// <summary> 
    /// It is used to restrict to create the instance of the  ImageCompress 
    /// </summary> 
    private ImageCompress() 
    { 
    } 
    #endregion[Constructor] 

    #region[Poperties] 
    /// <summary> 
    /// Gets ImageCompress object 
    /// </summary> 
    public static ImageCompress GetImageCompressObject 
    { 
     get 
     { 
      if (imageCompress == null) 
      { 
       imageCompress = new ImageCompress(); 
      } 
      return imageCompress; 
     } 
    } 

    /// <summary> 
    /// Gets or sets Width 
    /// </summary> 
    public int Height 
    { 
     get { return height; } 
     set { height = value; } 
    } 

    /// <summary> 
    /// Gets or sets Width 
    /// </summary> 
    public int Width 
    { 
     get { return width; } 
     set { width = value; } 
    } 

    /// <summary> 
    /// Gets or sets Image 
    /// </summary> 
    public Bitmap GetImage 
    { 
     get { return bitmap; } 
     set { bitmap = value; } 
    } 
    #endregion[Poperties] 

    #region[PublicFunction] 
    /// <summary> 
    /// This function is used to save the image 
    /// </summary> 
    /// <param name="fileName"></param> 
    /// <param name="path"></param> 
    public void Save(string fileName, string path) 
    { 
     if (ISValidFileType(fileName)) 
     { 
      string pathaname = path + @"\" + fileName; 
      save(pathaname, 60); 
     } 
    } 
    #endregion[PublicFunction] 

    #region[PrivateData] 
    /// <summary> 
    /// This function is use to compress the image to 
    /// predefine size 
    /// </summary> 
    /// <returns>return bitmap in compress size</returns> 
    private Image CompressImage() 
    { 
     if (GetImage != null) 
     { 
      Width = (Width == 0) ? GetImage.Width : Width; 
      Height = (Height == 0) ? GetImage.Height : Height; 
      Bitmap newBitmap = new Bitmap(Width, Height, PixelFormat.Format24bppRgb); 
      newBitmap = bitmap; 
      newBitmap.SetResolution(80, 80); 
      return newBitmap.GetThumbnailImage(Width, Height, null, IntPtr.Zero); 
     } 
     else 
     { 
      throw new Exception("Please provide bitmap"); 
     } 
    } 

    /// <summary> 
    /// This function is used to check the file Type 
    /// </summary> 
    /// <param name="fileName">String data type:contain the file name</param> 
    /// <returns>true or false on the file extention</returns> 
    private bool ISValidFileType(string fileName) 
    { 
     bool isValidExt = false; 
     string fileExt = Path.GetExtension(fileName); 
     switch (fileExt.ToLower()) 
     { 
      case CommonConstant.JPEG: 
      case CommonConstant.BTM: 
      case CommonConstant.JPG: 
      case CommonConstant.PNG: 
       isValidExt = true; 
       break; 
     } 
     return isValidExt; 
    } 

    /// <summary> 
    /// This function is used to get the imageCode info 
    /// on the basis of mimeType 
    /// </summary> 
    /// <param name="mimeType">string data type</param> 
    /// <returns>ImageCodecInfo data type</returns> 
    private ImageCodecInfo GetImageCoeInfo(string mimeType) 
    { 
     ImageCodecInfo[] codes = ImageCodecInfo.GetImageEncoders(); 
     for (int i = 0; i < codes.Length; i++) 
     { 
      if (codes[i].MimeType == mimeType) 
      { 
       return codes[i]; 
      } 
     } 
     return null; 
    } 
    /// <summary> 
    /// this function is used to save the image into a 
    /// given path 
    /// </summary> 
    /// <param name="path">string data type</param> 
    /// <param name="quality">int data type</param> 
    private void save(string path, int quality) 
    { 
     img = CompressImage(); 
     ////Setting the quality of the picture 
     EncoderParameter qualityParam = 
      new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality); 
     ////Seting the format to save 
     ImageCodecInfo imageCodec = GetImageCoeInfo("image/jpeg"); 
     ////Used to contain the poarameters of the quality 
     EncoderParameters parameters = new EncoderParameters(1); 
     parameters.Param[0] = qualityParam; 
     ////Used to save the image to a given path 
     img.Save(path, imageCodec, parameters); 
    } 
    #endregion[PrivateData] 
} 
} 

在这里，我上传图像与jQuery和Web服务的帮助下，我路过作为formdata文件

[WebMethod] 
    public void UploadFile() 
    { 
     if (HttpContext.Current.Request.Files.AllKeys.Any()) 
     { 
      // Get the uploaded image from the Files collection 
      var httpPostedFile = HttpContext.Current.Request.Files["UploadedImage"]; 
      if (httpPostedFile != null) 
      { 
       ImageCompress imgCompress = ImageCompress.GetImageCompressObject; 
       imgCompress.GetImage = new System.Drawing.Bitmap(httpPostedFile.InputStream); 
       imgCompress.Height = 260; 
       imgCompress.Width = 358; 
       //imgCompress.Save(httpPostedFile.FileName, @"C:\Documents and Settings\Rasmi\My Documents\Visual Studio2008\WebSites\compressImageFile\Logo"); 
       imgCompress.Save(httpPostedFile.FileName, HttpContext.Current.Server.MapPath("~/Download/")); 

      } 
     } 
    }