使用ImageResizer的Azure C＃WebJob未正确设置内容类型

Question

我正在使用Azure WebJob来调整新上载的图像的大小。调整大小的作品，但新创建的图像没有在Blob存储中正确设置其内容类型。相反，它们被列为application/octet-stream。这里处理调整大小的代码：

public static void ResizeImagesTask(
    [BlobTrigger("input/{name}.{ext}")] Stream inputBlob, 
    string name, 
    string ext, 
    IBinder binder) 
{ 
    int[] sizes = { 800, 500, 250 }; 
    var inputBytes = inputBlob.CopyToBytes(); 
    foreach (var width in sizes) 
    { 
     var input = new MemoryStream(inputBytes); 
     var output = binder.Bind<Stream>(new BlobAttribute($"output/{name}-w{width}.{ext}", FileAccess.Write)); 

     ResizeImage(input, output, width); 
    } 
} 

private static void ResizeImage(Stream input, Stream output, int width) 
{ 
    var instructions = new Instructions 
    { 
     Width = width, 
     Mode = FitMode.Carve, 
     Scale = ScaleMode.Both 
    }; 
    ImageBuilder.Current.Build(new ImageJob(input, output, instructions)); 
} 

我的问题是在哪里以及如何设置内容类型？这是我必须手动执行的操作，还是在我如何使用库时出现错误，以防止它分配与原始内容类型相同的内容类型（库说它应该显示的行为）？

谢谢！

最后更新

感谢托马斯，他在最后的解决方案帮助来到这里啊！

public class Functions 
{ 
    // output blolb sizes 
    private static readonly int[] Sizes = { 800, 500, 250 }; 

    public static void ResizeImagesTask(
     [QueueTrigger("assetimage")] AssetImage asset, 
     string container, 
     string name, 
     string ext, 
     [Blob("{container}/{name}_master.{ext}", FileAccess.Read)] Stream blobStream, 
     [Blob("{container}")] CloudBlobContainer cloudContainer) 
    { 

     // Get the mime type to set the content type 
     var mimeType = MimeMapping.GetMimeMapping($"{name}_master.{ext}"); 

     foreach (var width in Sizes) 
     { 
      // Set the position of the input stream to the beginning. 
      blobStream.Seek(0, SeekOrigin.Begin); 

      // Get the output stream 
      var outputStream = new MemoryStream(); 
      ResizeImage(blobStream, outputStream, width); 

      // Get the blob reference 
      var blob = cloudContainer.GetBlockBlobReference($"{name}_{width}.{ext}"); 

      // Set the position of the output stream to the beginning. 
      outputStream.Seek(0, SeekOrigin.Begin); 
      blob.UploadFromStream(outputStream); 

      // Update the content type => don't know if required 
      blob.Properties.ContentType = mimeType; 
      blob.SetProperties(); 
     } 
    } 

    private static void ResizeImage(Stream input, Stream output, int width) 
    { 
     var instructions = new Instructions 
     { 
      Width = width, 
      Mode = FitMode.Carve, 
      Scale = ScaleMode.Both 
     }; 
     var imageJob = new ImageJob(input, output, instructions); 

     // Do not dispose the source object 
     imageJob.DisposeSourceObject = false; 
     imageJob.Build(); 
    } 

    public static void PoisonErrorHandler([QueueTrigger("webjobs-blogtrigger-poison")] BlobTriggerPosionMessage message, TextWriter log) 
    { 
     log.Write("This blob couldn't be processed by the original function: " + message.BlobName); 
    } 
} 

public class AssetImage 
{ 
    public string Container { get; set; } 

    public string Name { get; set; } 

    public string Ext { get; set; } 
} 

public class BlobTriggerPosionMessage 
{ 
    public string FunctionId { get; set; } 
    public string BlobType { get; set; } 
    public string ContainerName { get; set; } 
    public string BlobName { get; set; } 
    public string ETag { get; set; } 
} 

Answer 1

你不能从你的实现设定的内容类型：

您需要访问CloudBlockBlob.Properties.ContentType属性：

CloudBlockBlob blob = new CloudBlockBlob(...); 
blob.Properties.ContentType = "image/..."; 
blob.SetProperties(); 

Azure的Webjob SDK中支持BLOB绑定，这样就可以直接绑定到一个blob。

在您的上下文中，您希望绑定到输入blob并创建多个输出blob。

• 使用BlobTriggerAttribute作为输入。
• 使用BlobTriggerAttribute绑定到您的输出blob。因为要创建多个输出blob，所以可以直接绑定到输出容器。

您的触发功能的代码可以看起来像：

using System.IO; 
using System.Web; 
using ImageResizer; 
using Microsoft.Azure.WebJobs; 
using Microsoft.WindowsAzure.Storage.Blob; 

public class Functions 
{ 
    // output blolb sizes 
    private static readonly int[] Sizes = {800, 500, 250}; 

    public static void ResizeImage(
     [BlobTrigger("input/{name}.{ext}")] Stream blobStream, string name, string ext 
     , [Blob("output")] CloudBlobContainer container) 
    { 
     // Get the mime type to set the content type 
     var mimeType = MimeMapping.GetMimeMapping($"{name}.{ext}"); 
     foreach (var width in Sizes) 
     { 
      // Set the position of the input stream to the beginning. 
      blobStream.Seek(0, SeekOrigin.Begin); 

      // Get the output stream 
      var outputStream = new MemoryStream(); 
      ResizeImage(blobStream, outputStream, width); 

      // Get the blob reference 
      var blob = container.GetBlockBlobReference($"{name}-w{width}.{ext}"); 

      // Set the position of the output stream to the beginning. 
      outputStream.Seek(0, SeekOrigin.Begin); 
      blob.UploadFromStream(outputStream); 

      // Update the content type 
      blob.Properties.ContentType = mimeType; 
      blob.SetProperties(); 
     } 
    } 

    private static void ResizeImage(Stream input, Stream output, int width) 
    { 
     var instructions = new Instructions 
     { 
      Width = width, 
      Mode = FitMode.Carve, 
      Scale = ScaleMode.Both 
     }; 
     var imageJob = new ImageJob(input, output, instructions); 

     // Do not dispose the source object 
     imageJob.DisposeSourceObject = false; 
     imageJob.Build(); 
    } 
} 

注意ImageJob对象上使用DisposeSourceObject的，这样我们就可以读取多个时间BLOB流。

此外，你应该有一个关于BlobTrigger看看Webjob文档：How to use Azure blob storage with the WebJobs SDK

的WebJobs SDK扫描日志文件来监视新的或改变的斑点。这个过程不是实时的;一个函数可能不会触发，直到blob创建后几分钟或更长时间。另外，还有storage logs are created on a "best efforts"的基础;不保证所有事件都将被捕获。在某些情况下，日志可能会丢失。如果blob触发器的速度和可靠性限制不适用于您的应用程序，则建议的方法是在创建blob时创建队列消息，并在处理blob的函数上使用QueueTrigger属性而不是BlobTrigger属性。

因此，可以更好地触发从队列中的消息，只是发送的文件名，你可以输入斑点自动绑定到消息队列：

using System.IO; 
using System.Web; 
using ImageResizer; 
using Microsoft.Azure.WebJobs; 
using Microsoft.WindowsAzure.Storage.Blob; 

public class Functions 
{ 
    // output blolb sizes 
    private static readonly int[] Sizes = { 800, 500, 250 }; 

    public static void ResizeImagesTask1(
     [QueueTrigger("newfileuploaded")] string filename, 
     [Blob("input/{queueTrigger}", FileAccess.Read)] Stream blobStream, 
     [Blob("output")] CloudBlobContainer container) 
    { 
     // Extract the filename and the file extension 
     var name = Path.GetFileNameWithoutExtension(filename); 
     var ext = Path.GetExtension(filename); 

     // Get the mime type to set the content type 
     var mimeType = MimeMapping.GetMimeMapping(filename); 

     foreach (var width in Sizes) 
     { 
      // Set the position of the input stream to the beginning. 
      blobStream.Seek(0, SeekOrigin.Begin); 

      // Get the output stream 
      var outputStream = new MemoryStream(); 
      ResizeImage(blobStream, outputStream, width); 

      // Get the blob reference 
      var blob = container.GetBlockBlobReference($"{name}-w{width}.{ext}"); 

      // Set the position of the output stream to the beginning. 
      outputStream.Seek(0, SeekOrigin.Begin); 
      blob.UploadFromStream(outputStream); 

      // Update the content type => don't know if required 
      blob.Properties.ContentType = mimeType; 
      blob.SetProperties(); 
     } 
    } 

    private static void ResizeImage(Stream input, Stream output, int width) 
    { 
     var instructions = new Instructions 
     { 
      Width = width, 
      Mode = FitMode.Carve, 
      Scale = ScaleMode.Both 
     }; 
     var imageJob = new ImageJob(input, output, instructions); 

     // Do not dispose the source object 
     imageJob.DisposeSourceObject = false; 
     imageJob.Build(); 
    } 
}