Running in Azure App Service

using System.IO;
class Config
{
    // Connecting string to blob container
    public static readonly string ConnectionString = "your_connection_string";
    // HOME_EXPANDED directory is common for all WebJobs folder
    public static readonly string LibraryFolder = Path.Combine(System.Environment.GetEnvironmentVariable("HOME_EXPANDED"), "FRE");
    // Input and output containers name in your storage
    public static readonly string LibraryContainerName = "fre-lib";

namespace FreDeployerJob
{
    public class Functions
    {
        // This function won't be triggered automatically - you should do it manually
        [NoAutomaticTrigger]
        [Timeout("01:00:00")]
        public static void DeployFRE()
        {
            Console.WriteLine("Deploying FRE");
            // Connecting to existing input container <InputContainerName> via Storage Account connection string
            BlobContainerClient inputContainerClient = new BlobContainerClient(Config.ConnectionString, Config.LibraryContainerName);
            // Creating library directory as well as AppData and Temp folders for ABBYY FineReader Engine initialization
            if (Directory.Exists(Config.LibraryFolder) == true)
            {
                Directory.Delete(Config.LibraryFolder, true);
            }
            Directory.CreateDirectory(Config.LibraryFolder);
            Directory.CreateDirectory(Path.Combine(Config.LibraryFolder, "Temp"));
            Directory.CreateDirectory(Path.Combine(Config.LibraryFolder, "AppData"));
            // Iterating via blobs in container. Blob in <InputContainerName> is equal to some image file
            foreach (BlobItem blobItem in inputContainerClient.GetBlobs())
            {
                Console.WriteLine("\t" + blobItem.Name);
                // Searching for light version of the ABBYY FineReader Engine library
                if (blobItem.Name == "LibraryPackage.zip")
                {
                    Console.WriteLine("LibraryPackage.zip was found.");
                    // Connecting to blob to access its contents
                    BlobClient blobClient = new BlobClient(Config.ConnectionString, Config.LibraryContainerName, blobItem.Name);
                    Console.WriteLine("Downloading to memory...");
                    // Download zip to memory
                    using (MemoryStream memoryStream = new MemoryStream())
                    {
                        blobClient.DownloadTo(memoryStream);
                        Console.WriteLine("LibraryPackage.zip was downloaded.");
                        Console.WriteLine("Unzipping...");
                        // Unzip without using temp folder (only memory processing)
                        using (ZipArchive archive = new ZipArchive(memoryStream))
                        {
                            foreach (ZipArchiveEntry entry in archive.Entries)
                            {
                                string subDirectory = Path.GetDirectoryName(Path.Combine(Config.LibraryFolder, entry.FullName));
                                if (Directory.Exists(subDirectory) == false)
                                {
                                    Directory.CreateDirectory(subDirectory);
                                }
                                if (entry.Name.Length != 0)
                                {
                                    entry.ExtractToFile(Path.Combine(subDirectory, entry.Name));
                                }
                            }
                        }
                        Console.WriteLine("LibraryPackage.zip was unzipped to HOME_EXPANDED.");
                    }
                }
            }
        }
    }
}

namespace FreDeployerJob
{
    // To learn more about Microsoft Azure WebJobs SDK, please see https://go.microsoft.com/fwlink/?LinkID=320976
    class Program
    {
        // Please set the following connection strings in app.config for these WebJobs to run:
        // AzureWebJobsDashboard and AzureWebJobsStorage
        static void Main()
        {
            // When triggered this WebJob will only call this method
            Functions.DeployFRE();
        }
    }
}

using System;
using System.IO;
namespace FreProcessorJob
{
    class Config
    {
        // Connecting string to blob container
        public static readonly string ConnectionString = "your_connection_string";
        // HOME_EXPANDED directory is common for all WebJobs folders
        // It is the same as in FreDeployerJob project
        public static readonly string LibraryFolder = Path.Combine(System.Environment.GetEnvironmentVariable("HOME_EXPANDED"), "FRE");
        // Processing container name in your storage
        public static readonly string ProcessingContainerName = "processing-container";
        // Processing queue name
        public static readonly string ProcessingQueueName = "processing-queue";
        public static readonly string StatusQueueName = "status-queue";
        // Return Customer Project ID for ABBYY FineReader Engine
        public static String GetCustomerProjectId()
        {
            return "your_cpid";
        }
 
        // Return name of online license token
        // If you don't use online license, leave an empty string
        // Token should be located in Bin64 folder of library package
        public static String GetLicenseTokenName()
        {
            return "your_online_license_token_if_you_have_it";
        }
 
        // Return online license password
        // If you don't use online license, leave an empty string
        public static String GetLicensePassword()
        {
            return "online_license_password_if_you have_it";
        }
 
        // Return name of license token
        // Licensing is located in Bin64 folder of the library package
        public static String GetLicenseTokenName()
        {
            return "your_licence_for_ABBYY FineReader Engine";
        }
 
        // Return license password
        public static String GetLicensePassword()
        {
            return "license_password";
        }
 
        // Return engine path
        public static String GetEngineFolder()
        {
            string engineSubfolder = "Bin64";
            string engineDllFolder = Path.Combine(LibraryFolder, engineSubfolder);
            return engineDllFolder;
        }
    }
}

using Microsoft.Azure.WebJobs;
using System;
using System.IO;
using Azure.Storage.Blobs;
using Azure.Storage.Queues;
using Newtonsoft.Json.Linq;
namespace FreProcessorJob
{
    public class Functions
    {
        // This function will get triggered/executed when a new message is written
        // on an Azure Queue called processing-queue
        // The message is expected to be a JSON message with 'blob-item-name' key
        // processing results will be saved to processing container
        // processing status will be sent to status-queue in JSON format
        public static void ProcessQueueMessage([QueueTrigger("processing-queue")] string message)
        {
            // First of all, connecting to status-queue
            QueueClient queueClient = new QueueClient(Config.ConnectionString, Config.StatusQueueName);
            try
            {
                // This will be logged to WebJob logs on Azure portal
                Console.WriteLine("Accepted task: " + message);
                JObject task = JObject.Parse(message);
                task["processor_id"] = Environment.GetEnvironmentVariable("WEBJOBS_NAME");
 
                // This will be send to status-queue
                task["status"] = "accepted";
                queueClient.SendMessage(task.ToString());
 
                // Getting blob-item-name - the name of file in Processing container
                string blobFileName = task["blob-item-name"].ToString();
                BlobClient blobClient = new BlobClient(Config.ConnectionString, Config.ProcessingContainerName, blobFileName);
                // Loading blob into memory
                Console.WriteLine("\t Downloading blob to memory: " + blobFileName);
                MemoryStream memoryStream = new MemoryStream();
                blobClient.DownloadTo(memoryStream);
                Console.WriteLine("\t Downloaded.");
                // Updating status to processing
                Console.WriteLine("\t Processing in FRE: " + blobFileName);
                task["status"] = "processing";
                queueClient.SendMessage(task.ToString());
                // Processing the downloaded blob in ABBYY FineReader Engine using memory processing methods
                // The output is the name of processing result saved as blob in <ProcessingContainerName>
                string resultBlobName = "";
                using (FreProcessor.Processor freProcessor = new FreProcessor.Processor())
                {
                    resultBlobName = freProcessor.ProcessBlobFromMemory(memoryStream, blobFileName);
                    Console.WriteLine("\t Result blob name in output container: " + resultBlobName);
                }
                // Deleting input image
                Console.WriteLine("\t Deleting from input container: " + blobFileName);
                blobClient.Delete();
                // Updating status to succeeded
                // in Azure portal logs
                Console.WriteLine("Succeeded");
 
                // in status-queue
                task["status"] = "succeeded";
                task["result-blob-name"] = resultBlobName;
                queueClient.SendMessage(task.ToString());
            }
            catch (Exception error)
            {
                // In case of any errors reporting
                // to Azure portal logs
                Console.WriteLine("Failed: " + error.Message);
                // to status-queue
                JObject task = new JObject(); 
                task["processor_id"] = Environment.GetEnvironmentVariable("WEBJOBS_NAME");
                task["status"] = "failed";
                task["error"] = error.Message;
                task["task"] = message;
                queueClient.SendMessage(task.ToString());
            }
        }
    }
}

using Microsoft.Azure.WebJobs;
namespace FreProcessorJob
{
    // To learn more about Microsoft Azure WebJobs SDK, please see https://go.microsoft.com/fwlink/?LinkID=320976
    class Program
    {
        // Please set the following connection strings in app.config for these WebJobs to run:
        // AzureWebJobsDashboard and AzureWebJobsStorage
        static void Main()
        {
            var config = new JobHostConfiguration();
            if (config.IsDevelopment)
            {
                config.UseDevelopmentSettings();
            }
            // ABBYY FineReader Engine is not thread-safe, so we cannot process more than one message simultaneously
            config.Queues.BatchSize = 1;
            var host = new JobHost(config);
            // The following code ensures that the WebJob will be running continuously
            // as one of functions is attached to Azure queue and listens for new tasks
            host.RunAndBlock();
        }
    }
}

using System;
using System.IO;
using System.Runtime.InteropServices;
using FREngine;
namespace FreProcessorJob.FreProcessor
{
    // Class for loading/unloading FREngine.dll and initializing/deinitializing Engine
    // Loading is performed in constructor, unloading in Dispose()
    // Throws exceptions when loading fails
    public class EngineLoader : IDisposable
    {
        // Load ABBYY FineReader Engine with settings stored in SamplesConfig.cs
        public EngineLoader()
        {
            string enginePath = Path.Combine(Config.GetEngineFolder(), "FREngine.dll");
            string customerProjectId = Config.GetCustomerProjectId();
            string licensePath = Path.Combine(Config.GetEngineFolder(), Config.GetLicenseTokenName());
            string licensePassword = Config.GetLicensePassword();
            try
            {
                // Load the FREngine.dll library
                dllHandle = LoadLibraryEx(enginePath, IntPtr.Zero, LOAD_WITH_ALTERED_SEARCH_PATH);
                if (dllHandle == IntPtr.Zero)
                {
                    int error = Marshal.GetLastWin32Error();
                    Console.WriteLine("The last Win32 Error was: " + error);
                    throw new Exception("Can't load " + enginePath);
                }
 
                IntPtr initializeEnginePtr = GetProcAddress(dllHandle, "InitializeEngine");
                if (initializeEnginePtr == IntPtr.Zero)
                {
                    throw new Exception("Can't find InitializeEngine function");
                }
                IntPtr deinitializeEnginePtr = GetProcAddress(dllHandle, "DeinitializeEngine");
                if (deinitializeEnginePtr == IntPtr.Zero)
                {
                    throw new Exception("Can't find DeinitializeEngine function");
                }
                IntPtr dllCanUnloadNowPtr = GetProcAddress(dllHandle, "DllCanUnloadNow");
                if (dllCanUnloadNowPtr == IntPtr.Zero)
                {
                    throw new Exception("Can't find DllCanUnloadNow function");
                }
                // Convert pointers to delegates
                initializeEngine = (InitializeEngine)Marshal.GetDelegateForFunctionPointer(
                    initializeEnginePtr, typeof(InitializeEngine));
                deinitializeEngine = (DeinitializeEngine)Marshal.GetDelegateForFunctionPointer(
                    deinitializeEnginePtr, typeof(DeinitializeEngine));
                dllCanUnloadNow = (DllCanUnloadNow)Marshal.GetDelegateForFunctionPointer(
                    dllCanUnloadNowPtr, typeof(DllCanUnloadNow));
                // Call the InitializeEngine function
                string dataFolder = Path.Combine(Config.LibraryFolder, "AppData");
                string tempFolder = Path.Combine(Config.LibraryFolder, "Temp");
                int hresult = initializeEngine(customerProjectId, licensePath, licensePassword,
                    dataFolder, tempFolder, false, ref engine);
                Marshal.ThrowExceptionForHR(hresult);
            }
            catch (Exception)
            {
                // Free the FREngine.dll library
                engine = null;
                // Deleting all objects before FreeLibrary call
                GC.Collect();
                GC.WaitForPendingFinalizers();
                GC.Collect();
                FreeLibrary(dllHandle);
                dllHandle = IntPtr.Zero;
                initializeEngine = null;
                deinitializeEngine = null;
                dllCanUnloadNow = null;
                throw;
            }
        }
        // Unload ABBYY FineReader Engine
        public void Dispose()
        {
            if (engine == null)
            {
                // Engine was not loaded
                return;
            }
            engine = null;
            int hresult = deinitializeEngine();
            // Deleting all objects before FreeLibrary call
            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();
            hresult = dllCanUnloadNow();
            if (hresult == 0)
            {
                FreeLibrary(dllHandle);
            }
            dllHandle = IntPtr.Zero;
            initializeEngine = null;
            deinitializeEngine = null;
            dllCanUnloadNow = null;
            // throwing exception after cleaning up
            Marshal.ThrowExceptionForHR(hresult);
        }
        // Returns pointer to ABBYY FineReader Engine's main object
        public IEngine Engine
        {
            get
            {
                return engine;
            }
        }
        // Kernel32.dll functions
        [DllImport("kernel32.dll")]
        private static extern IntPtr LoadLibraryEx(string dllToLoad, IntPtr reserved, uint flags);
        private const uint LOAD_WITH_ALTERED_SEARCH_PATH = 0x00000008;
        [DllImport("kernel32.dll")]
        private static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName);
        [DllImport("kernel32.dll")]
        private static extern bool FreeLibrary(IntPtr hModule);
        // FREngine.dll functions
        [UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Unicode)]
        private delegate int InitializeEngine(string customerProjectId, string licensePath, string licensePassword,
            string dataFolder, string tempFolder, bool isSharedCPUCoresMode, ref FREngine.IEngine engine);
        [UnmanagedFunctionPointer(CallingConvention.StdCall)]
        private delegate int DeinitializeEngine();
        [UnmanagedFunctionPointer(CallingConvention.StdCall)]
        private delegate int DllCanUnloadNow();
        // private variables
        private FREngine.IEngine engine = null;
        // Handle to FREngine.dll
        private IntPtr dllHandle = IntPtr.Zero;
        private InitializeEngine initializeEngine = null;
        private DeinitializeEngine deinitializeEngine = null;
        private DllCanUnloadNow dllCanUnloadNow = null;
    }
}

using System;
using System.IO;
using Azure.Storage.Blobs;
namespace FreProcessorJob.FreProcessor
{
    public class FileWriter : FREngine.IFileWriter, IDisposable
    {
        public FileWriter(string _resultBlobName, string _fileExtension)
        {
            resultBlobName = _resultBlobName;
            fileExtension = _fileExtension;
        }
        public void Open(string fileName, ref int bufferSize)
        {
            stream = new MemoryStream();
        }
        public void Write(byte[] data)
        {
            stream.Write(data, 0, data.Length);
        }
        public void Close()
        {
            // Creating connection to new blob in <ProcessingContainerName>. The processing result will be stored there
            BlobClient resultBlobClient = new BlobClient(Config.ConnectionString, 
                Config.ProcessingContainerName,
                resultBlobName + fileExtension);
            // Rewrite existing file
            resultBlobClient.DeleteIfExists();
            // Setting position to 0 to write file from beginning
            stream.Position = 0;
            resultBlobClient.Upload(stream);
            stream.Close();
        }
        public void Dispose()
        {
            // Closing memory stream on disposal to be able to access it after data was written
            stream.Close();
        }
        private string resultBlobName;
        private string fileExtension;
        private MemoryStream stream;
    }
}

using System;
using System.Runtime.InteropServices;
using System.IO;
using FREngine;
namespace FreProcessorJob.FreProcessor
{
    class Processor : IDisposable
    {
        private EngineLoader engineLoader = null;
        private void displayMessage(string text)
        {
            Console.WriteLine("\t" + text);
        }
        private void setupFREngine()
        {
            displayMessage("Loading predefined profile...");
            // this is optional
            engineLoader.Engine.LoadPredefinedProfile("DocumentConversion_Accuracy");
            // this is mandatory on low-performing App Service Plans as we will be getting errors on parallel processing
            engineLoader.Engine.MultiProcessingParams.MultiProcessingMode = MultiProcessingModeEnum.MPM_Sequential;
        }
        private void LoadEngine()
        {
            try
            {
                if (engineLoader == null)
                {
                    engineLoader = new EngineLoader();
                }
                setupFREngine();
            }
            catch (Exception error)
            {
                displayMessage("error: " + error.Message);
            }
        }
        private void UnloadEngine()
        {
            try
            {
                if (engineLoader != null)
                {
                    engineLoader.Dispose();
                    engineLoader = null;
                }
            }
            catch (Exception error)
            {
                displayMessage("error: " + error.Message);
            }
        }
        public Processor()
        {
            LoadEngine();
        }
        public string ProcessBlobFromMemory(MemoryStream inputMemoryStream, string inputBlobName)
        {
            FRDocument document = engineLoader.Engine.CreateFRDocument();
            string resultBlobName = "";
            try
            {
                document.PageFlushingPolicy = FREngine.PageFlushingPolicyEnum.PFP_KeepInMemory;
 
                // Add image file to document
                displayMessage("Loading image...");
                IntPtr handle = Marshal.AllocHGlobal(inputMemoryStream.GetBuffer().Length);
                Marshal.Copy(inputMemoryStream.GetBuffer(), 0, handle, inputMemoryStream.GetBuffer().Length);
                document.AddImageFileFromMemory(handle.ToInt64(), null, null);
                // Recognize the document
                displayMessage("Recognizing...");
                document.Process(null);
                // Save results
                displayMessage("Saving results...");
                FileWriter fileWriter = new FileWriter(inputBlobName, ".pdf");
                resultBlobName = inputBlobName + ".pdf";
                document.ExportToMemory(fileWriter, FREngine.FileExportFormatEnum.FEF_PDF, null);
            }
            catch (Exception error)
            {
                displayMessage("error: " + error.Message);
                throw error;
            }
            finally
            {
                // Close the document
                document.Close();
            }
            return resultBlobName;
        }
        public void Dispose()
        {
            UnloadEngine();
        }
    }
}