在 Azure Functions 应用程序 blobtrigger 中设置 blob 的内容类型

Question

我正在尝试调整上传到我的容器的图像的大小，以便为我的网站创建缩略图和其他各种版本的图像。

我上传的图片必须更正内容类型“image/jpeg”，但是当我使用下面的代码创建它们的新版本时，结果显示为“application/octet-stream”。

我在这里错过了什么？

using ImageResizer;
using ImageResizer.ExtensionMethods;
 
public static void Run(Stream myBlob, string blobname, string blobextension, Stream outputBlob, TraceWriter log)
{
    log.Info($"C# Blob trigger function Processed blob\n Name:{blobname} \n Size: {myBlob.Length} Bytes");
    
    var instructions = new Instructions
    {
        Width = 570,
        Mode = FitMode.Crop,
        Scale = ScaleMode.Both,
    };
    ImageBuilder.Current.Build(new ImageJob(myBlob, outputBlob, instructions));
}

编辑：解决方案。

#r "Microsoft.WindowsAzure.Storage"
using ImageResizer;
using ImageResizer.ExtensionMethods;
using Microsoft.WindowsAzure.Storage.Blob;

public static void Run(Stream myBlob, string blobname, string blobextension, CloudBlockBlob outputBlob, TraceWriter log)
{
    log.Info($"C# Blob trigger function Processed blob\n Name:{blobname} \n Size: {myBlob.Length} Bytes");
    
    var instructions = new Instructions
    {
        Width = 570,
        Mode = FitMode.Crop,
        Scale = ScaleMode.Both
    };

    Stream stream = new MemoryStream();
    ImageBuilder.Current.Build(new ImageJob(myBlob, stream, instructions));
    stream.Seek(0, SeekOrigin.Begin);
 
    outputBlob.Properties.ContentType = "image/jpeg";
    outputBlob.UploadFromStream(stream);
}

Answer 1

当您使用流输出时，函数会将您的内容类型默认为 application/octet-stream。

使用其中一种 ICloudBlob 类型，它应该允许您指定 blob 的内容类型。

这是一个可以作为参数绑定到的类型的备忘单：https://jhaleyfiles2016.blob.core.windows.net/public/Azure%20WebJobs%20SDK%20Cheat%20Sheet%202014.pdf

Answer 2

这是一个调整图像大小的 Azure 函数的完整工作示例：

run.csx

#r "Microsoft.WindowsAzure.Storage"

using Microsoft.WindowsAzure.Storage.Blob;
using ImageResizer;
using ImageResizer.ExtensionMethods;

public static void Run(Stream imageStream, string blobName, CloudBlockBlob outputBlob, TraceWriter log)
{
    log.Info($"Function triggered by blob\n Name:{blobName} \n Size: {imageStream.Length} Bytes");

    var instructions = new Instructions
    {
        Width = 400,
        Height = 350,
        Mode = FitMode.Max,
        OutputFormat = OutputFormat.Jpeg,
        JpegQuality = 85
    };

    using (var outputStream = new MemoryStream())
    {
        ImageBuilder.Current.Build(new ImageJob(imageStream, outputStream, instructions));
        outputStream.Position = 0;
        outputBlob.Properties.ContentType = "image/jpeg";
        outputBlob.UploadFromStream(outputStream);
    }
}

function.json

{
  "bindings": [
    {
      "name": "imageStream",
      "type": "blobTrigger",
      "direction": "in",
      "path": "watched-container/{blobName}.jpg",
      "connection": "AzureWebJobsDashboard"
    },
    {
      "type": "blob",
      "name": "outputBlob",
      "path": "output-container/{blobName}.jpg",
      "connection": "AzureWebJobsDashboard",
      "direction": "inout"
    }
  ],
  "disabled": false
}

project.json

{
"frameworks": {
  "net46":{
    "dependencies": {
      "ImageResizer": "4.0.5"
    }
  }
 }
}