Using ABBYY FineReader Engine in C (Objective-C)

/* C */
#define __RPC__deref_out
#define COBJMACROS
#include <FREngine.h>
/* Objective-C */
#define interface _COM_interface
#define __RPC__deref_out
#define COBJMACROS
#import <FREngine.h>
#undef interface

typedef HRESULT (*initializeEngine_ptr) (BSTR, BSTR, BSTR, BSTR, BSTR, VARIANT_BOOL, IEngine **);
typedef HRESULT (*DeinitializeEngine_ptr) (void);
static IEngine* FREngine;
static HMODULE FREngineDll;
int main(int argc, char *argv[]) {
 initializeEngine InitializeEngine=NULL;
 DeinitializeEngine_ptr DeinitializeEngine=NULL;
 // provide your Customer Project ID here, and if applicable, the Online License information
 wchar_t *customerProjectId = L"";
 wchar_t *licensePath = L"";
 wchar_t *licensePassword = L"";
 FREngineDll = LoadLibraryEx("<path to FREngine.dll>", 0, LOAD_WITH_ALTERED_SEARCH_PATH);
 if(FREngineDll) {
  InitializeEngine = (InitializeEngine_ptr) GetProcAddress(FREngineDll,"InitializeEngine");
  if(InitializeEngine)
   InitializeEngine(customerProjectId, licensePath, licensePassword, "", "", FALSE, &FREngine);
 }
 ProcessImage();
 IEngine_Release( FREngine );
 DeinitializeEngine = (DeinitializeEngine_ptr) GetProcAddress(FREngineDll,"DeinitializeEngine");
 DeinitializeEngine();
}

void ProcessImage()
{
 IFRDocument* frDocument = NULL;
 IEngine_CreateFRDocument( FREngine, &frDocument );
 IFRDocument_AddImageFile( frDocument, L"<path to a source image>", NULL, NULL );
 IFRDocument_Process( frDocument, NULL, NULL, NULL );
 IFRDocument_Export( frDocument, L"<path to an output file>", FEF_PDF, NULL );
 IFRDocument_Release( frDocument );
}