improve Tesseract performance with OpenCV on Android

Question

I am working on a Android application using real-time OCR. I using OpenCV and Tesseract Library. But the performance is very poor, even on my Galaxy SIII. There are any meth

Answer 1

Use multithreading, but be aware to create one instance per thread for TessBaseAPI. Don't share them between different threads. Create N threads (N >= number of cores), and java will make sure that you speed up at least the number of cores times.

What I do is creating N threads which create TessBaseAPI objects in their own context (in the run method) and wait for OCR requests in a loop until interrupted.

    ...
    ...
    @Override
    public void run() {

      TessBaseAPI tessBaseApi = new TessBaseAPI();

      tessBaseApi.init(Ocrrrer.DATA_PATH, "eng");

      setTessVariable(tessBaseApi, "load_system_dawg", "0");
      setTessVariable(tessBaseApi, "load_freq_dawg", "0");
      setTessVariable(tessBaseApi, "load_unambig_dawg", "0");
      setTessVariable(tessBaseApi, "load_punc_dawg", "0");
      setTessVariable(tessBaseApi, "load_number_dawg", "0");
      setTessVariable(tessBaseApi, "load_fixed_length_dawgs", "0");
      setTessVariable(tessBaseApi, "load_bigram_dawg", "0");
      setTessVariable(tessBaseApi, "wordrec_enable_assoc", "0");
      setTessVariable(tessBaseApi, "tessedit_enable_bigram_correction", "0");
      setTessVariable(tessBaseApi, "assume_fixed_pitch_char_segment", "1");
      setTessVariable(tessBaseApi, TessBaseAPI.VAR_CHAR_WHITELIST, "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ<");

      Log.d(TAG, "Training file loaded");


      while (!interrupted()) {
        reentrantLock.lock();
        try {
          Log.d(TAG, this.getName() + " wait for OCR");
          jobToDo.await();
          Log.d(TAG, this.getName() + " input arrived. Do OCR");
          this.ocrResult = doOcr(tessBaseApi);
          ocrDone.signalAll();
        } catch (InterruptedException e) {
          return;
        } finally {
          try {
            reentrantLock.unlock();
          } catch (Exception ex) {
          }
        }
      }

    }
    ...
    ...

You can see that the tessBaseApi object is local to the run method, hence absolutely not shared.