圖片上傳有很多情況需要考慮，例如：生成縮略圖、壓縮尺寸、壓縮質量、壓縮尺寸質量、添加水印等等常見情況。最近遇到圖片質量壓縮不改變大小的問題，參考：聽浪
#region 圖片壓縮
/// <summary>
/// 圖片壓縮(降低質量以減小文件的大小)
/// </summary>
/// <param name="srcBitMap">傳入的Bitmap對象</param>
/// <param name="destFile">壓縮后的圖片保存路徑</param>
/// <param name="level">壓縮等級，0到100，0 最差質量，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>
/// 編碼信息
/// </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>
/// 圖片壓縮(降低質量以減小文件的大小)
/// </summary>
/// <param name="srcBitmap">傳入的Bitmap對象</param>
/// <param name="destStream">壓縮后的Stream對象</param>
/// <param name="level">壓縮等級，0到100，0 最差質量，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 給定的 quality level
myEncoderParameter = new EncoderParameter(myEncoder, level);
myEncoderParameters.Param[0] = myEncoderParameter;
srcBitmap.Save(destStream, myImageCodecInfo, myEncoderParameters);
}
#endregion