I'm trying to make an android application that do real time ocr and then
put the result text on the corresponding text areas.
The libraries I used is:
OpenCV4android 3.1.0.
tess-two(https://github.com/rmtheis/tess-two)
The target language is: English.(I use eng.traineddata)
I've been testing it on my tablet(asus memo pad7).
The text-detection part is good enough, but the ocr part is no better than
gibberish and the frame rate drops.
I want to know if there is a method to improve
I did searched several articles to find a way to improve ocr result, but
none of these worked.
I'm very confident that the real time ocr is possible, because 2 years ago
I saw this video <https://www.youtube.com/watch?v=4IKoxb_pbLo>
I've been studying his code for over 6 months and finally made my way here.
But there is a striking difference between the OCR result of my app and his
work.
I will keep trying to contact the author.
But he is now starting a new company at Japan and it seems that he will
have any time to deal with my problem.
Therefore I post this question here, hoping anyone could give me some help.
The following is my code to detect text and do ocr:
public class TextDetector implements Filter{
Bitmap bmp=null;
TessBaseAPI baseApi = new TessBaseAPI();
public String ocr(Mat tmp){
baseApi.init("/mnt/sdcard/tesseract/", "eng");
baseApi.setPageSegMode(TessBaseAPI.PageSegMode.PSM_SINGLE_LINE);
bmp=Bitmap.createBitmap(tmp.cols(), tmp.rows(),
Bitmap.Config.ARGB_8888);
Utils.matToBitmap(tmp, bmp);
baseApi.setImage(bmp);
return baseApi.getUTF8Text();
}
@Override
public void apply(Mat src, Mat dst) {
if (dst != src) {
src.copyTo(dst);
}
//this text detection method is translated from
http://stackoverflow.com/questions/23506105/extracting-text-opencv
Mat img_gray,img_sobel, img_threshold, element;
//turn source image to gray scale
img_gray=new Mat();
Imgproc.cvtColor(src, img_gray, Imgproc.COLOR_RGB2GRAY);
//sobel edge detection
img_sobel=new Mat();
Imgproc.Sobel(img_gray, img_sobel, CvType.CV_8U, 1, 0, 3, 1,
0,Core.BORDER_DEFAULT);
//thresholding
img_threshold=new Mat();
Imgproc.threshold(img_sobel, img_threshold, 0, 255,
Imgproc.THRESH_OTSU+Imgproc.THRESH_BINARY);
//removing noise
element=new Mat();
element = Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(17,
3) );
Imgproc.morphologyEx(img_threshold, img_threshold, Imgproc.MORPH_CLOSE,
element);
//extract contours
List<MatOfPoint> contours=new ArrayList<MatOfPoint>();
Mat hierarchy = new Mat();
Imgproc.findContours(img_threshold, contours, hierarchy, 0, 1);
List<MatOfPoint> contours_poly=new
ArrayList<MatOfPoint>(contours.size());
//for opencv4android only. you have to turn the List<MatOfPoint> into
MatOfPoint2f
//to run the approxPolyDP function. then turn it back into
List<MatOfPoint>
contours_poly.addAll(contours);
MatOfPoint2f mMOP2f1,mMOP2f2;
mMOP2f1=new MatOfPoint2f();
mMOP2f2=new MatOfPoint2f();
//
for( int i = 0; i < contours.size(); i++ )
if (contours.get(i).toList().size()>100)
{
contours.get(i).convertTo(mMOP2f1, CvType.CV_32FC2);
Imgproc.approxPolyDP(mMOP2f1,mMOP2f2, 3, true );
mMOP2f2.convertTo(contours_poly.get(i), CvType.CV_32S);
Rect appRect=Imgproc.boundingRect(contours_poly.get(i));
if (appRect.width>appRect.height)
{
Imgproc.rectangle(dst, new Point(appRect.x,appRect.y) ,new
Point(appRect.x+appRect.width,appRect.y+appRect.height), new
Scalar(255,0,0));
Log.i(null, "cut Roi");
Mat roiMat=new Mat(src,appRect);
Log.i(null, "OCR and puttext");
Imgproc.putText(dst,ocr(roiMat), new
Point(appRect.x,appRect.y),Core.FONT_HERSHEY_SIMPLEX, 1, new
Scalar(0,255,0));
Log.i(null, "Complete!");
}
}
}
}
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