C#上传图片压缩质量，不改变尺寸

图片上传有很多情况需要考虑，例如：生成缩略图、压缩尺寸、压缩质量、压缩尺寸质量、添加水印等等常见情况。最近遇到图片质量压缩不改变大小的问题，参考：听浪

#region 图片压缩
/// <summary>
/// 图片压缩(降低质量以减小文件的大小)
/// </summary>
/// <param name="srcBitMap">传入的Bitmap对象</param>
/// <param name="destFile">压缩后的图片保存路径</param>
/// <param name="level">压缩等级，0到100，0 最差质量，100 最佳</param>
public static void Compress(Bitmap srcBitMap, string destFile, long level)
{
    Stream s = new FileStream(destFile, FileMode.Create);
    Compress(srcBitMap, s, level);
    s.Close();
}

/// <summary>
/// 编码信息
/// </summary>
/// <param name="mimeType"></param>
/// <returns></returns>
private static ImageCodecInfo GetEncoderInfo(String mimeType)
{
    int j;
    ImageCodecInfo[] encoders;
    encoders = ImageCodecInfo.GetImageEncoders();
    for (j = 0; j < encoders.Length; ++j)
    {
        if (encoders[j].MimeType == mimeType)
            return encoders[j];
    }
    return null;
}

/// <summary>
/// 图片压缩(降低质量以减小文件的大小)
/// </summary>
/// <param name="srcBitmap">传入的Bitmap对象</param>
/// <param name="destStream">压缩后的Stream对象</param>
/// <param name="level">压缩等级，0到100，0 最差质量，100 最佳</param>
private static void Compress(Bitmap srcBitmap, Stream destStream, long level)
{
    ImageCodecInfo myImageCodecInfo;
    Encoder myEncoder;
    EncoderParameter myEncoderParameter;
    EncoderParameters myEncoderParameters;
    // Get an ImageCodecInfo object that represents the JPEG codec.
    myImageCodecInfo = GetEncoderInfo("image/jpeg");
    // Create an Encoder object based on the GUID
    // for the Quality parameter category.
    myEncoder = 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.
    myEncoderParameters = new EncoderParameters(1);
    // Save the bitmap as a JPEG file with 给定的 quality level
    myEncoderParameter = new EncoderParameter(myEncoder, level);
    myEncoderParameters.Param[0] = myEncoderParameter;
    srcBitmap.Save(destStream, myImageCodecInfo, myEncoderParameters);
}
#endregion

参考：听浪 http://www.cnblogs.com/ainidewen/p/4556543.html