Extracting Text From An Image Using Azure Cognitive Services

static async Task ExtractTextUsingOCR(string imageFilePath)
{
    try
    {
        HttpClient client = new HttpClient();

        // Request headers.
        client.DefaultRequestHeaders.Add("Ocp-Apim-Subscription-Key", subscriptionKey);                
        string requestParameters = "language=unk&detectOrientation=true";
        
        string uri = uriBase + "?" + requestParameters;
        HttpResponseMessage response;

        // Read image into a byte array
        byte[] dataBytes = GetByteArrayOfImage(imageFilePath);

        // Add the byte array as an octet stream to the request body.
        using (ByteArrayContent content = new ByteArrayContent(dataBytes))
        {
            content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

            // Call to API
            response = await client.PostAsync(uri, content);
        }
       
        string contentString = await response.Content.ReadAsStringAsync();

        // Display output
        Console.WriteLine("\nResponse:\n\n{0}\n", JToken.Parse(contentString).ToString());
    }
    catch (Exception e)
    {
        Console.WriteLine("\n" + e.Message);
    }
}
    
static byte[] GetByteArrayOfImage(string imageFilePath)
{
    // Open a read-only file stream for the specified file.
    using (FileStream fs = new FileStream(imageFilePath, FileMode.Open, FileAccess.Read))
    {
        BinaryReader binaryReader = new BinaryReader(fs);
        return binaryReader.ReadBytes((int)fs.Length);
    }
}

Sample Code for reading API

static async Task ExtractTextUsingReadAPI(string imageFilePath)
{
    try
    {
        HttpResponseMessage response;
        HttpClient client = new HttpClient();

        // request headers
        client.DefaultRequestHeaders.Add("Ocp-Apim-Subscription-Key", subscriptionKey);
        string url = uriBase;
                        
        // operationLocation stores the URI of the second REST API method,
        // returned by the first REST API method.
        string operationLocation;

        byte[] dataBytes = GetByteArrayOfImage(imageFilePath);               
        using (ByteArrayContent content = new ByteArrayContent(dataBytes))
        {
            content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

            // first method
            response = await client.PostAsync(url, content);
        }
        
        if (response.IsSuccessStatusCode)
            operationLocation = response.Headers.GetValues("Operation-Location").FirstOrDefault();
        else
        {
            string errorContent = await response.Content.ReadAsStringAsync();
            Console.WriteLine("\n\nResponse:\n{0}\n", JToken.Parse(errorContent).ToString());
            return;
        }
       
        string contentString;
        int i = 0;
        do
        {
            System.Threading.Thread.Sleep(1000);

            // second method
            response = await client.GetAsync(operationLocation);
            contentString = await response.Content.ReadAsStringAsync();
            ++i;
        }
        while (i < 30 && contentString.IndexOf("\"status\":\"succeeded\"") == -1);

        if (i == 30 && contentString.IndexOf("\"status\":\"succeeded\"") == -1)
        {
            Console.WriteLine("\nTimeout happened.\n");
            return;
        }

        // Display output content
        Console.WriteLine("\nResponse:\n\n{0}\n", JToken.Parse(contentString).ToString());
    }
    catch (Exception e)
    {
        Console.WriteLine("\n" + e.Message);
    }
}

static byte[] GetByteArrayOfImage(string imageFilePath)
{
    // Open a read-only file stream for the specified file.
    using (FileStream fileStream =
        new FileStream(imageFilePath, FileMode.Open, FileAccess.Read))
    {
        // Read the file's contents into a byte array.
        BinaryReader binaryReader = new BinaryReader(fileStream);
        return binaryReader.ReadBytes((int)fileStream.Length);
    }
}

Do watch out for the attached video for the demo and code walk-through here.

Happy learning!