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

Question

我正在处理 Azure WebJob 以调整新上传图像的大小。调整大小有效，但新创建的图像在 Blob 存储中没有正确设置其内容类型。相反，它们被列为 application/octet-stream。这里是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？这是我必须手动做的事情，还是我使用库的方式有误，阻止它分配与原始内容类型相同的内容类型（库说它应该表现出的行为）？

谢谢！

最终更新

感谢 Thomas 帮助得出最终解决方案，就在这里！

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

您无法从您的实现中设置内容类型：

您需要访问 CloudBlockBlob.Properties.ContentType 属性:

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

Azure Webjob SDK 支持 Blob 绑定，因此您可以直接绑定到 blob。

在您的上下文中，您想绑定到一个输入 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。

触发函数的代码可能如下所示：

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();
    }
}

注意在 ImageJob 对象上使用 DisposeSourceObject 以便我们可以多次读取 blob 流。

此外，您应该查看有关 BlobTrigger 的 Webjob 文档：How to use Azure blob storage with the WebJobs SDK

The WebJobs SDK scans log files to watch for new or changed blobs. This process is not real-time; a function might not get triggered until several minutes or longer after the blob is created. In addition, storage logs are created on a "best efforts" basis; there is no guarantee that all events will be captured. Under some conditions, logs might be missed. If the speed and reliability limitations of blob triggers are not acceptable for your application, the recommended method is to create a queue message when you create the blob, and use the QueueTrigger attribute instead of the BlobTrigger attribute on the function that processes the blob.

因此最好从只发送文件名的队列中触发消息，您可以将输入 blob 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();
    }
}

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

Azure C# WebJob using ImageResizer not Properly Setting Content-Type

c#

azure

azure-webjobs