服务器上 GetThumbnailImage 中的 C# 内存不足异常

Question

当用户向我们发送图像时，我正在运行以下代码来创建缩略图:

public int AddThumbnail(byte[] originalImage, File parentFile)
    {
        File tnFile = null;
        try
        {
            System.Drawing.Image image;
            using (System.IO.MemoryStream memoryStream = new System.IO.MemoryStream(originalImage))
            {
                image = System.Drawing.Image.FromStream(memoryStream);
            }
            Log.Write("Original image width of [" + image.Width.ToString() + "] and height of [" + image.Height.ToString() + "]");
            //dimensions need to be changeable
            double factor = (double)m_thumbnailWidth / (double)image.Width;

            int thHeight = (int)(image.Height * factor);
            byte[] tnData = null;
            Log.Write("Thumbnail width of [" + m_thumbnailWidth.ToString() + "] and height of [" + thHeight + "]");
            using (System.Drawing.Image thumbnail = image.GetThumbnailImage(m_thumbnailWidth, thHeight, () => false, IntPtr.Zero))
            {                    
                using (System.IO.MemoryStream tnStream = new System.IO.MemoryStream())
                {
                    thumbnail.Save(tnStream, System.Drawing.Imaging.ImageFormat.Jpeg);
                    tnData = new byte[tnStream.Length];
                    tnStream.Position = 0;
                    tnStream.Read(tnData, 0, (int)tnStream.Length);
                }
            }
//there is other code here that is not relevant to the problem

        }
        catch (Exception ex)
        {
            Log.Error(ex);
        }

        return (tnFile == null ? -1 : tnFile.Id);
    }

这在我的机器上运行良好，但是当我在测试服务器上运行它时，我总是在该行出现内存不足异常: 使用 (System.Drawing.Image thumbnail = image.GetThumbnailImage(m_thumbnailWidth, thHeight, () => false, IntPtr.Zero))它不是在处理大图像:它试图将 480*640 图像转换为 96*128 缩略图。我不知道如何调查/解决这个问题。有人有什么建议吗？它总是发生，即使在我重新启动 IIS 之后也是如此。我最初确实认为图像可能已损坏，但尺寸是正确的。谢谢。

Answer 1

我们在 ASP.Net 服务器中使用 GDI+ 操作时也遇到了类似的问题。你提到你的代码在服务器上运行让我想到，这可能是同一个问题。

请注意，服务器不支持在 System.Drawing 命名空间中使用类。致命的是，它可能会工作一段时间，然后突然(即使没有更改代码)出现错误。

我们不得不重写服务器代码的重要部分。

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Caution note

Classes within the System.Drawing namespace are not supported for use within a Windows or ASP.NET service. Attempting to use these classes from within one of these application types may produce unexpected problems, such as diminished service performance and run-time exceptions. For a supported alternative, see Windows Imaging Components.

来源: http://msdn.microsoft.com/de-de/library/system.drawing(v=vs.110).aspx