Tesseract-OCR example of C-API: produce pdf output

/**********************************************************************

  Example of C-API: produce output with ResultRenderer

  gcc capi-example-renderer_pdf.c -o capi-example-renderer_pdf -ltesseract -llept -Wall
  ./capi-example-renderer_pdf && cat ./capi-test.txt

**********************************************************************/

#include "tesseract/capi.h"
#include "leptonica/allheaders.h"

int main(int argc, char **argv) {
    const char* lang = "eng";
    const char* image = "../tesseract-ocr/testing/phototest.tif";
    const char* output = "capi-test";
    const char* tessdata = "/usr/src/tesseract-ocr/";

    TessBaseAPI*  api;
    TessResultRenderer* renderer = NULL;
    int ret;

    api = TessBaseAPICreate();
    TessBaseAPISetOutputName(api, output);

    ret = TessBaseAPIInit3(api, tessdata, lang);

    if (ret) {
        TessBaseAPIDelete(api);
        fprintf(stderr, "Could not initialize tesseract.\n");
        exit(1);
    }

    const char* api_tessdata = TessBaseAPIGetDatapath(api);
    TessBaseAPISetVariable(api, "tessedit_create_pdf", "T");
    renderer = TessPDFRendererCreate(output, api_tessdata);

    PIX *pix_image = pixRead(image);

    const char* retry_config = NULL;
    int timeout_millisec = 0;
    int page = 0;

    const char* kUnknownTitle = "";
    if (renderer && !TessResultRendererBeginDocument(renderer, kUnknownTitle)) {
      pixDestroy(&pix_image);
      return 1;
    }

   int r = 0;
   r = TessBaseAPIProcessPage(api,
                                 pix_image,  // struct Pix* pix,
                                 page,       //int page_index,
                                 image,     // const char* filename,
                                 retry_config,  // const char* retry_config,
                                 timeout_millisec,  // int timeout_millisec
                                 renderer     // TessResultRenderer* renderer
                                 );
    pixDestroy(&pix_image);

    if (!r || (renderer && !TessResultRendererEndDocument(renderer))) {
      return 2;
    }
    TessBaseAPIDelete(api);
    return 0;                      // Normal exit
}