/// <summary>
/// Submits an image for OCR analysis. The analysis is async, so a second call needs to be made to retrieve the results.
/// </summary>
/// <param name="imageAsBytes">the image to process, as a byte array</param>
/// <returns>url where the result of analysis can be found. or null.</returns>
/// <remarks>
/// Method requires a Response 202 from initial image response
/// The service has accepted the request and will start processing later.
/// It will return Accepted immediately and include an "Operation-Location" header.
/// Client side should further query the read operation status using the URL specified in this header.
/// The operation ID will expire in 48 hours.
/// </remarks>
private async Task <string> MakeOcrAnalysisRequestToAzure(byte[] imageAsBytes)
{
using (var client = new HttpClient())
{
try
{
client.DefaultRequestHeaders.Add("Ocp-Apim-Subscription-Key", ConnectionDetails.SubscriptionKey);
var url = ConnectionDetails.GetOcrUrl();
HttpResponseMessage response;
using (ByteArrayContent content = new ByteArrayContent(imageAsBytes))
{
content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
response = await client.PostAsync(url, content);
}
// Operation-Location is the URI where the results can be found. There will only be 1 value here, but .NET doesn't let us do this quickly.
if (response.Headers.TryGetValues("Operation-Location", out var headerValues))
{
return(headerValues.FirstOrDefault());
}
}
catch (HttpRequestException ex)
{
Console.WriteLine(ex);
throw;
}
}
return(null);
}
/// <summary>
/// Submits an image for OCR analysis. The analysis is async, so a second call needs to be made to retrieve the results.
/// </summary>
/// <param name="imageByteArray">the image to process, as a byte array</param>
/// <returns>url where the result of analysis can be found. or null.</returns>
/// <remarks>
/// Method requires a Response 202 from initial image response
/// The service has accepted the request and will start processing later.
/// It will return Accepted immediately and include an "Operation-Location" header.
/// Client side should further query the read operation status using the URL specified in this header.
/// The operation ID will expire in 48 hours.
/// </remarks>
private string MakeOcrAnalysisRequestToAzure(byte[] imageByteArray)
{
string callbackUrl = null;
HttpWebResponse response = null;
try
{
var request = WebRequest.CreateHttp(new Uri(ConnectionDetails.GetOcrUrl()));
request.ContentType = "application/octet-stream";
request.Headers.Add("Ocp-Apim-Subscription-Key", ConnectionDetails.SubscriptionKey);
request.Method = "POST";
request.ContentLength = imageByteArray.Length;
var requestStream = request.GetRequestStream();
requestStream.Write(imageByteArray, 0, imageByteArray.Length);
requestStream.Close();
response = (HttpWebResponse)request.GetResponse();
if (response.StatusCode != HttpStatusCode.OK)
{
throw new HttpRequestException("did not return success");
}
callbackUrl = response.Headers["Operation-Location"];
}
catch (HttpRequestException ex)
{
Console.WriteLine(ex);
throw;
}
finally
{
response?.Close();
}
return(callbackUrl);
}