Bitmap读取本地高分辨率图片报内存不足的解决方案

 1 #region getThumImage 生成缩略图
 2         /// <summary>
 3         /// 生成缩略图
 4         /// </summary>
 5         /// <param name="sourceFile">原始图片文件</param>
 6         /// <param name="quality">质量压缩比</param>
 7         /// <param name="multiple">收缩倍数</param>
 8         /// <param name="outputFile">输出文件名</param>
 9         /// <param name="DPI">水平分辨率、垂直分辨率</param>
10         /// <returns>成功返回true,失败则返回false</returns>
11         public bool getThumImage(String sourceFile, long quality, int multiple, String outputFile, int DPI)
12         {
13             try
14             {
15                 long imageQuality = quality;
16                 Bitmap sourceImage = new Bitmap(sourceFile);
17                 ImageCodecInfo myImageCodecInfo = GetEncoderInfo("image/jpeg");
18                 System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
19                 EncoderParameters myEncoderParameters = new EncoderParameters(1);
20                 EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, imageQuality);
21                 myEncoderParameters.Param[0] = myEncoderParameter;
22                 float xWidth = sourceImage.Width;
23                 float yWidth = sourceImage.Height;
24                 Bitmap newImage = new Bitmap((int)(xWidth / multiple), (int)(yWidth / multiple));
25                 newImage.SetResolution(DPI, DPI);
26                 Graphics g = Graphics.FromImage(newImage);
27 
28                 g.DrawImage(sourceImage, 0, 0, xWidth / multiple, yWidth / multiple);
29                 sourceImage.Dispose();
30                 g.Dispose();
31                 newImage.Save(outputFile, myImageCodecInfo, myEncoderParameters);
32                 return true;
33             }
34             catch
35             {
36                 return false;
37             }
38         }
39         #endregion getThumImage

改进后代码

 1 #region getThumImage 生成缩略图
 2         /// <summary>
 3         /// 生成缩略图
 4         /// </summary>
 5         /// <param name="sourceFile">原始图片文件</param>
 6         /// <param name="quality">质量压缩比</param>
 7         /// <param name="multiple">收缩倍数</param>
 8         /// <param name="outputFile">输出文件名</param>
 9         /// <param name="DPI">水平分辨率、垂直分辨率</param>
10         /// <returns>成功返回true,失败则返回false</returns>
11         public bool getThumImage(String sourceFile, long quality, int multiple, String outputFile, int DPI)
12         {
13             try
14             {
15                 long imageQuality = quality;
16                 #region 用流方式来读取图片，避开内存不足问题。
17                 FileStream fileStream = new FileStream(sourceFile, FileMode.Open, FileAccess.Read, FileShare.Read);//打开文件
18                 byte[] bytes = new byte[fileStream.Length];//读取文件的byte[]
19                 fileStream.Read(bytes, 0, bytes.Length);
20                 fileStream.Close();
21                 Stream stream = new MemoryStream(bytes);//把byte[]转换成Stream
22                 stream.Read(bytes, 0, bytes.Length);
23                 stream.Seek(0, SeekOrigin.Begin);//设置当前流的位置为流的开始                
24                 Bitmap sourceImage = new Bitmap((Image)new Bitmap(stream));
25                 #endregion
26                 ImageCodecInfo myImageCodecInfo = GetEncoderInfo("image/jpeg");
27                 System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
28                 EncoderParameters myEncoderParameters = new EncoderParameters(1);
29                 EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, imageQuality);
30                 myEncoderParameters.Param[0] = myEncoderParameter;
31                 float xWidth = sourceImage.Width;
32                 float yWidth = sourceImage.Height;
33                 Bitmap newImage = new Bitmap((int)(xWidth / multiple), (int)(yWidth / multiple));
34                 newImage.SetResolution(DPI, DPI);
35                 Graphics g = Graphics.FromImage(newImage);
36 
37                 g.DrawImage(sourceImage, 0, 0, xWidth / multiple, yWidth / multiple);
38                 sourceImage.Dispose();
39                 g.Dispose();
40                 newImage.Save(outputFile, myImageCodecInfo, myEncoderParameters);
41                 return true;
42             }
43             catch (Exception ex)
44             {
45                 GC.Collect();
46                 string message = ex.Message;
47                 MessageBox.Show("Error: " + message);
48                 return false;
49             }
50             finally
51             {
52                 GC.Collect();
53             }
54         }
55         #endregion getThumImage

主要改进是在下面这段用流的方式来读取文件，主要可以绕过内存不足的报错

 1 #region 用流方式来读取图片，避开内存不足问题。
 2 FileStream fileStream = new FileStream(sourceFile, FileMode.Open, FileAccess.Read, FileShare.Read);//打开文件
 3 byte[] bytes = new byte[fileStream.Length];//读取文件的byte[]
 4 fileStream.Read(bytes, 0, bytes.Length);
 5 fileStream.Close();
 6 Stream stream = new MemoryStream(bytes);//把byte[]转换成Stream
 7 stream.Read(bytes, 0, bytes.Length);
 8 stream.Seek(0, SeekOrigin.Begin);//设置当前流的位置为流的开始
 9 Bitmap sourceImage = new Bitmap((Image)new Bitmap(stream));
10 #endregion