asp.net：GDI+ 中发生一般错误

Question

我创建了一个 asp.net 4.0 Web 应用程序，它具有用于上传图像的 Web 服务。我通过将 Base64 字符串形式的图像从我的移动应用程序发送到 Web 服务来上传图像。

以下是我的代码：

public string Authenticate(string username, string password, string fileID, string imageData)
    {
        Dictionary<string, string> responseDictionary = new Dictionary<string, string>();
        bool isAuthenticated = true; // Set this value based on the authentication logic

        try
        {
            if (isAuthenticated)
            {
                UploadImage(imageData);

                string result = "success";
                var message = "Login successful";

                responseDictionary["status"] = result;
                responseDictionary["message"] = message;
            }
        }
        catch (Exception ex)
        {

            responseDictionary["status"] = ex.Message;
            responseDictionary["message"] = ex.StackTrace;
        }

        return new JavaScriptSerializer().Serialize(responseDictionary);
    }

    private void UploadImage(string uploadedImage)
    {
        // Convert Base64 String to byte[]
        byte[] imageBytes = Convert.FromBase64String(uploadedImage);
        MemoryStream ms = new MemoryStream(imageBytes, 0, imageBytes.Length);

        System.Drawing.Bitmap bitmap = (System.Drawing.Bitmap)Image.FromStream(ms);

        string uploadPath = Server.MapPath("..\\uploads\\") + DateTime.Now.Ticks.ToString() + ".jpeg";
        ms.Close();

        bitmap.Save(uploadPath, System.Drawing.Imaging.ImageFormat.Jpeg);
        bitmap.Dispose();
    }    

这段代码在我的本地 ASP.NET 开发服务器上运行良好，我能够在我的“上传”目录中看到上传的图像。但是，将代码传输到 FTP 目录后，我现在收到以下错误：

A generic error occurred in GDI+

我通过创建一个虚拟 .aspx 页面并在 page_load 上创建一个文本文件来检查上传目录是否具有适当的权限，并且它工作正常。

即使在谷歌搜索之后，我也无法解决这个问题。谁能帮我解决这个问题？

非常感谢。

Answer 1

此外，我认为值得指出的是，当使用 MemoryStream 时，必须始终关闭流并且 save 方法必须在流关闭之前调用

 byte[] byteBuffer = Convert.FromBase64String(Base64String);
 MemoryStream memoryStream = new MemoryStream(byteBuffer);
 memoryStream.Position = 0;
 Bitmap bmpReturn = (Bitmap)Bitmap.FromStream(memoryStream);
 bmpReturn.Save(PicPath, ImageFormat.Jpeg);
 memoryStream.Close();

Answer 2

不要直接写入文件，而是将位图保存到MemoryStream，然后将流的内容保存到磁盘。这是一个古老的已知问题，坦率地说，我不记得为什么会这样的所有细节。

 MemoryStream mOutput = new MemoryStream();
 bmp.Save( mOutput, ImageFormat.Png );
 byte[] array = mOutput.ToArray();

 // do whatever you want with the byte[]

在你的情况下，它可能是

private void UploadImage(string uploadedImage)
{
    // Convert Base64 String to byte[]
    byte[] imageBytes = Convert.FromBase64String(uploadedImage);

    string uploadPath = Server.MapPath("..\\uploads\\") + DateTime.Now.Ticks.ToString() + ".jpeg";

    // store the byte[] directly, without converting to Bitmap first 
    using ( FileStream fs = File.Create( uploadPath ) )
    using ( BinaryWriter bw = new BinaryWriter( fs ) )
       bw.Write( imageBytes );
}    

或

private void UploadImage(string uploadedImage)
{
    // Convert Base64 String to byte[]
    byte[] imageBytes = Convert.FromBase64String(uploadedImage);
    MemoryStream ms = new MemoryStream(imageBytes, 0, imageBytes.Length);

    System.Drawing.Bitmap bitmap = (System.Drawing.Bitmap)Image.FromStream(ms);

    string uploadPath = Server.MapPath("..\\uploads\\") + DateTime.Now.Ticks.ToString() + ".jpeg";
    ms.Close();

    // convert to image first and store it to disk
    using ( MemoryStream mOutput = new MemoryStream() )
    {  
        bitmap.Save( mOutput, System.Drawing.Imaging.ImageFormat.Jpeg);
        using ( FileStream fs = File.Create( uploadPath ) )
        using ( BinaryWriter bw = new BinaryWriter( fs ) )
            bw.Write( mOutput.ToArray() );
    }
}