How does the Tesseract variable “save_blob_choices” works (in tess-two)?

[Sergio Mendoza]

So I've been trying to use tesseract ocr, (specifically tess-two) for an android project to scan some symbols.

Everything works fine but sometimes the recognized String is returned as null. One of the solutions I found was to set the variable save_blob_choices to true in order to have tesseract save alternatives for recognition.

But I don't know if it indeed is supposed to do that. Where does it save the alternatives? How do I access them?

Of course if you have any other solution apart from using this variable, please tell me.

Here is my code:

TessBaseAPI baseApi = new TessBaseAPI();
baseApi.setDebug(true);
baseApi.init(MainActivity.DATA_PATH, MainActivity.lang);
baseApi.setPageSegMode(TessBaseAPI.PageSegMode.PSM_SINGLE_CHAR);


baseApi.setVariable("tessedit_char_whitelist","abcdefghijklmnopqrst");
baseApi.setVariable("save_blob_choices", "T");

baseApi.setImage(mainBitmap);

publishProgress(80);


mainBitmap.recycle();
mainBitmap = null;

// Iterate through the results.
ResultIterator iterator = baseApi.getResultIterator();
String lastUTF8Text;
float lastConfidence;


iterator.begin();
do {
    lastUTF8Text = iterator.getUTF8Text(TessBaseAPI.PageIteratorLevel.RIL_SYMBOL);
    lastConfidence = iterator.confidence(TessBaseAPI.PageIteratorLevel.RIL_SYMBOL);

    Log.i("string, intConfidence",lastUTF8Text+", "+lastConfidence);
} while (iterator.next(TessBaseAPI.PageIteratorLevel.RIL_SYMBOL));


baseApi.end();

Also as an extra question, is base.setDebug(true) supposed to work? Because it doesn't seem to do anything.

[zdenko podobny]

have a look at tesseract::ChoiceIterator.

See https://github.com/tesseract-ocr/tesseract/wiki/APIExample#example-of-iterator-over-the-classifier-choices-for-a-single-symbol

Zdenko

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[Tom Morris]

What version are you using? I don't see a save_blob_choices in the current sources and the two closest matches, save_alt_choices and save_raw_choices, don't actually appear to do anything.

Tom

[Sergio Mendoza]

I´m using tess-two which uses Tesseract v3.05.00dev. 

[Sergio Mendoza]

I think it could work, but I don't really know C++. Do you know if there is any place I could find this, but passed to Java? Like an update of the tess-two project or something like that. I wouldn't mind learning C++, but I'm running on the clock unfortunately.

[zdenko podobny]

I am not familiar with tess-two, but I see there function  getChoicesAndConfidence[1].

[1] https://github.com/rmtheis/tess-two/blob/master/tess-two/src/com/googlecode/tesseract/android/ResultIterator.java#L80

Zdenko

On Mon, Mar 14, 2016 at 7:12 PM, Sergio Mendoza <srgmet...@gmail.com> wrote:

I think it could work, but in the tess-two version that class is not passed to Java. Do you know if there is any place I could find it? (Problem is I don't reallly know C++)

On Monday, March 14, 2016 at 1:29:37 AM UTC-6, zdenop wrote:

To view this discussion on the web visit https://groups.google.com/d/msgid/tesseract-ocr/925421d2-737c-434e-9e2f-86091e975f88%40googlegroups.com.

[Sergio Mendoza]

Thanks that works, I'd already found that class, but I couldn't get it to work, because I didn't know what to pass as parameter.

FYI in tess-two the paramter is just defined as int level, which is any variable from TessBaseAPI.PageIteratorLevel.

In my case instead of _constant_name_ I had to pass RIL_SYMBOL so tess would recognize single characters.