Calculating skew of text OpenCV

Question

I am trying to calculate the skew of text in an image so I can correct it for the best OCR results.

Currently this is the function I am using:

doubl         


        

Answer 1

the approach you posted has its own "ideal binarization" assumption. the threshold value directly affects the process. utilize otsu threshold, or think about DFT for a generic solution.

otsu trial:

int main()
{
    Mat input = imread("your text");
    cvtColor(input, input, CV_BGR2GRAY);
    Mat img;
    cv::threshold(input, img, 100, 255, cv::THRESH_OTSU);

    cv::bitwise_not(img, img);
    imshow("img ", img);
    waitKey(0);

    vector points;
    findNonZero(img, points);
    cv::RotatedRect box = cv::minAreaRect(points);

    double angle = box.angle;
    if (angle < -45.)
        angle += 90.;

    cv::Point2f vertices[4];
    box.points(vertices);
    for(int i = 0; i < 4; ++i)
        cv::line(img, vertices[i], vertices[(i + 1) % 4], cv::Scalar(255, 0, 0));
    imshow("img ", img);
    waitKey(0);

    return 0;
}