An image service for retrieving images from Azure for ImageProcessor. Read more on https://piotrbach.com/configuring-umbraco-media-on-azure-private-blob-storage

imageprocessor-custom-azure-imageservice.txt

/// <summary>
/// An image service for retrieving images from Azure.
/// </summary>
public class AzureImageService : IImageService
{
   private CloudBlobContainer _blobContainer;
   private CloudStorageAccount _storageAccount;
   private Dictionary<string, string> _settings = new Dictionary<string, string>();

   /// <summary>
   /// Gets or sets the prefix for the given implementation.
   /// <remarks>
   /// This value is used as a prefix for any image requests that should use this service.
   /// </remarks>
   /// </summary>
   public string Prefix { get; set; } = string.Empty;

   /// <summary>
   /// Gets a value indicating whether the image service requests files from
   /// the locally based file system.
   /// </summary>
   public bool IsFileLocalService => false;

   /// <summary>
   /// Gets or sets any additional settings required by the service.
   /// </summary>
   public Dictionary<string, string> Settings
   {
      get => this._settings;
      set
      {
         this._settings = value;
         this.InitService();
      }
   }

   /// <summary>
   /// Gets or sets the white list of <see cref="Uri" />. 
   /// </summary>
   public Uri[] WhiteList { get; set; }

   /// <summary>
   /// Gets the image using the given identifier.
   /// </summary>
   /// <param name="id"></param>
   /// <returns></returns>
   public async Task<byte[]> GetImage(object id)
   {
      if (await _blobContainer.ExistsAsync())
      {
         //expecting id as "3gikqq22/example-image.png"
         string sId = PrepareBlobName(id);

         CloudBlockBlob blob = _blobContainer.GetBlockBlobReference(sId);

         if (await blob.ExistsAsync())
         {
            using (MemoryStream memoryStream = MemoryStreamPool.Shared.GetStream())
            {
               await blob.DownloadToStreamAsync(memoryStream).ConfigureAwait(false);
               return memoryStream.ToArray();
            }
         }
      }

      return null;
   }

   /// <summary>
   /// Removes container prefix from blob path
   /// </summary>
   /// <param name="id"></param>
   /// <returns></returns>
   private string PrepareBlobName(object id)
   {
      string sId = id.ToString();

      if (sId.StartsWith($"/{this.Settings["Container"]}/"))
      {
         return sId.Substring(this.Settings["Container"].Length + 2);
      }

      return sId;
   }


   /// <summary>
   /// Gets a value indicating whether the current request passes sanitizing rules.
   /// </summary>
   /// <param name="path">The image path.</param>
   /// <returns>
   /// <c>True</c> if the request is valid; otherwise, <c>False</c>.
   /// </returns>
   public bool IsValidRequest(string path) => ImageHelpers.IsValidImageExtension(path);

   /// <summary>
   /// Initialise the service.
   /// </summary>
   private void InitService()
   {
      // Retrieve storage accounts from connection string.
      _storageAccount = CloudStorageAccount.Parse(this.Settings["StorageAccount"]);

      // Create the blob client.
      CloudBlobClient blobClient = _storageAccount.CreateCloudBlobClient();

      string container = this.Settings.ContainsKey("Container")
         ? this.Settings["Container"]
         : string.Empty;

      BlobContainerPublicAccessType accessType = this.Settings.ContainsKey("AccessType")
         ? (BlobContainerPublicAccessType)Enum.Parse(typeof(BlobContainerPublicAccessType), this.Settings["AccessType"])
         : BlobContainerPublicAccessType.Blob;

      this._blobContainer = CreateContainer(blobClient, container, accessType);
   }

   /// <summary>
   /// Returns the cache container, creating a new one if none exists.
   /// </summary>
   /// <param name="cloudBlobClient"><see cref="CloudBlobClient"/> where the container is stored.</param>
   /// <param name="containerName">The name of the container.</param>
   /// <param name="accessType"><see cref="BlobContainerPublicAccessType"/> indicating the access permissions.</param>
   /// <returns>The <see cref="CloudBlobContainer"/></returns>
   private static CloudBlobContainer CreateContainer(CloudBlobClient cloudBlobClient, string containerName, BlobContainerPublicAccessType accessType)
   {
      CloudBlobContainer container = cloudBlobClient.GetContainerReference(containerName);

      if (!container.Exists())
      {
         container.Create();
         container.SetPermissions(new BlobContainerPermissions { PublicAccess = accessType });
      }

      return container;
   }
}