/*

This tutorial demonstrates how to correct the skewness in a text.

The program takes as input a skewed source image and shows non skewed text.

*/

#include <opencv2/core.hpp>

#include <opencv2/imgcodecs.hpp>

#include <opencv2/highgui.hpp>

#include <opencv2/imgproc.hpp>

#include <iostream>

#include <iomanip>

#include <string>

using namespace cv;

using namespace std;

int main( int argc, char** argv )

{

CommandLineParser parser(argc, argv, "{@input | imageTextR.png | input image}");

// Load image from the disk

Mat image = imread( samples::findFile( parser.get<String>("@input") ), IMREAD_COLOR);

if (image.empty())

{

cout << "Cannot load the image " + parser.get<String>("@input") << endl;

return -1;

}

Mat gray;

cvtColor(image, gray, COLOR_BGR2GRAY);

//Threshold the image, setting all foreground pixels to 255 and all background pixels to 0

Mat thresh;

threshold(gray, thresh, 0, 255, THRESH_BINARY_INV | THRESH_OTSU);

// Applying erode filter to remove random noise

int erosion_size = 1;

Mat element = getStructuringElement( MORPH_RECT, Size(2*erosion_size+1, 2*erosion_size+1), Point(erosion_size, erosion_size) );

erode(thresh, thresh, element);

cv::Mat coords;

findNonZero(thresh, coords);

RotatedRect box = minAreaRect(coords);

float angle = box.angle;

// The cv::minAreaRect function returns values in the range [-90, 0)

// if the angle is less than -45 we need to add 90 to it

if (angle < -45.0f)

{

angle = (90.0f + angle);

}

//Obtaining the rotation matrix

Point2f center((image.cols) / 2.0f, (image.rows) / 2.0f);

Mat M = getRotationMatrix2D(center, angle, 1.0f);

Mat rotated;

// Rotating the image by required angle

stringstream angle_to_str;

angle_to_str << fixed << setprecision(2) << angle;

warpAffine(image, rotated, M, image.size(), INTER_CUBIC, BORDER_REPLICATE);

putText(rotated, "Angle " + angle_to_str.str() + " degrees", Point(10, 30), FONT_HERSHEY_SIMPLEX, 0.7, Scalar(0, 0, 255), 2);

cout << "[INFO] angle: " << angle_to_str.str() << endl;

//Show the image

imshow("Input", image);

imshow("Rotated", rotated);

waitKey(0);

return 0;

}