Save a Image File from Blob Container in Azure

Introduction

Azure Blob storage is a service for storing large amounts of unstructured data. In this article we will look how we can save a Image File from Blob Container.

Step 1: Create a Source Blob Container in the Azure Portal

Open the Azure portal(https://portal.azure.com), and then choose Storage Account say Containers

Create a source container say sourcecontainer

It will appear as

Step 2: Upload a file in the Source Container

Let us upload an image file in sourcecontainer.

Step 3: Save a Image File from Blob Container programatically

Fire up a console application and add the below Nuget packages

Install-Package WindowsAzure.Storage

Install-Package Microsoft.WindowsAzure.ConfigurationManager

Next write the below function

/// <summary>
/// SaveBlobImage
/// Saves the blob image in local drive
/// </summary>
/// <param name="filename"></param>
/// <param name="connectionString"></param>
/// <param name="containerName"></param>
/// <returns></returns>
private static void SaveBlobImage(string filename, string connectionString, string containerName)
{
    // Retrieve storage account from connection string.
    CloudStorageAccount storageAccount = CloudStorageAccount.Parse(connectionString);

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

    // Retrieve reference to a previously created container.
    CloudBlobContainer container = blobClient.GetContainerReference(containerName);

    // Retrieve reference to a blob named "1.jpg"
    CloudBlockBlob blockBlobReference = container.GetBlockBlobReference(filename);
   
    using (var memoryStream = new MemoryStream())
    {
        //downloads blob's content to a stream
        blockBlobReference.DownloadToStream(memoryStream);

        //creates an image from the memory stream
        using (Image image = Image.FromStream(memoryStream))
        {
            //save the image
            image.Save("D:\\blobImage.jpg", ImageFormat.Jpeg);
        }
    }
}

The above function gets the blob's reference and using the DownloadToStream function, it downloads the blob's content to a memory stream. This stream of data is then converted to an image by the Image.FromStream function and it is saved in the local drive.

Now from inside the main function, let us write the below code

static void Main(string[] args)
{           
    string connectionString = CloudConfigurationManager.GetSetting("StorageConnectionString"); //blob connection string
    string sourceContainerName = ConfigurationManager.AppSettings["sourcecontainerName"]; //source blob container name           
    string sourceBlobFileName = "1.jpg"; //source blob name
    SaveBlobImage(sourceBlobFileName, connectionString, sourceContainerName);            
}

The program invokes the SaveBlobImage function to save the blob content as image.

The app.config file looks as under

  <appSettings>    
    <add key="StorageConnectionString" value="DefaultEndpointsProtocol=https;AccountName=testaccount;AccountKey=CRd****==;EndpointSuffix=core.windows.net" />   
    <add key="sourcecontainerName" value="sourcecontainer" />   
  </appSettings>

The complete program is as under

using Microsoft.Azure;
using Microsoft.WindowsAzure.Storage;
using Microsoft.WindowsAzure.Storage.Blob;
using System.Configuration;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

namespace UploadFilesToBlob
{
    class Program
    {
        static void Main(string[] args)
        {
          
            string connectionString = CloudConfigurationManager.GetSetting("StorageConnectionString"); //blob connection string
            string sourceContainerName = ConfigurationManager.AppSettings["sourcecontainerName"]; //source blob container name          
            string sourceBlobFileName = "1.jpg"; //source blob name
            SaveBlobImage(sourceBlobFileName, connectionString, sourceContainerName);            
        }

        private static void SaveBlobImage(string filename, string connectionString, string containerName)
        {
            // Retrieve storage account from connection string.
            CloudStorageAccount storageAccount = CloudStorageAccount.Parse(connectionString);

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

            // Retrieve reference to a previously created container.
            CloudBlobContainer container = blobClient.GetContainerReference(containerName);

            // Retrieve reference to a blob named "1.jpg"
            CloudBlockBlob blockBlobReference = container.GetBlockBlobReference(filename);
           
            using (var memoryStream = new MemoryStream())
            {
                //downloads blob's content to a stream
                blockBlobReference.DownloadToStream(memoryStream);

                //creates an image from the memory stream
                using (Image image = Image.FromStream(memoryStream))
                {
                    //save the image
                    image.Save("D:\\blobImage.jpg", ImageFormat.Jpeg);
                }
            }
        }              
    }
}

Conclusion

In this article we looked into how save an Image File from Blob Container. Hope this will be helpful. Thanks for reading. Zipped file attached.