Question

我正在使用Azure WebJob来调整新上传的图像的大小。调整大小有效，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，他们列出了application / octet-stream。这里是处理调整大小的代码：

{firstname=myname, address={}, phone={mobile2=123, mobile=4532134213131312, office=312321321312312, home=123213213213}, lastname=surname}

我的问题是我在哪里以及如何设置内容类型？这是我必须手动完成的事情，或者我是如何使用库来防止它分配与原始内容类型相同的内容类型（库应该表现出来的行为）？

谢谢！

最终更新

感谢托马斯在达成最终解决方案方面的帮助，这就是它！

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));
}

Answer 1

您无法从实施中设置内容类型：

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，以便您可以直接绑定到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绑定到输出blob。因为您想要创建多个输出blob，所以可以直接绑定到输出容器。

您触发的功能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();
    }
}

请注意在DisposeSourceObject对象上使用ImageJob，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

WebJobs SDK扫描日志文件以监视新的或更改的blob。这个过程不是实时的;在创建blob后几分钟或更长时间内，函数可能不会被触发。另外，storage logs are created on a "best efforts"基础;无法保证将捕获所有事件。在某些情况下，可能会错过日志。如果blob触发器的速度和可靠性限制对于您的应用程序是不可接受的，建议的方法是在创建blob时创建队列消息，并使用QueueTrigger属性而不是BlobTrigger属性处理blob的函数。

因此，从发送文件名的队列中触发消息可能会更好，您可以自动将输入blob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Content-Type

1 个答案: