How to crop image base boundingRect openCV?

See more:

C++

OpenCV

Hello, I write the code in detect license plate using openCV and C++. It's work.
Now I want to crop region in bounding rect. Please help me. Thanks.
Here is my code

#include <opencv\cv.h>
#include <opencv\highgui.h>
#include <opencv\ml.h>
#include <opencv\cxcore.h>

#include<opencv2/core/core.hpp>
#include<opencv2/highgui/highgui.hpp>
#include<opencv2/imgproc/imgproc.hpp>

#include <opencv2\imgcodecs.hpp>

#include <stdio.h>
#include <stdlib.h>
#include<iostream>
using namespace cv;
using namespace std;

//khai báo biến
cv::Mat _img;		// ảnh gốc
cv::Mat _imgGray;		// ảnh xám
//hàm main

int main()
{
	_img = cv::imread("bs9.jpg");			// mở ảnh gốc
	if (_img.empty()) {									// hàm báo không mở được ảnh
		std::cout << "error: image not read from file\n\n";
		return(0);
	}
	cv::Mat src;
	medianBlur(_img, src, 9);

	// chuyển ảnh gốc sang ảnh xám
	cv::cvtColor(src, _imgGray, CV_BGR2GRAY);
	cv::Mat _imgGray2;
	medianBlur(_imgGray, _imgGray, 7);
	blur(_imgGray, _imgGray, Size(3, 3));
	//Canny
	cv::Mat edges;
	//dalation

	//cv::Canny(_imgGray, edges, 100, 250);
	cv::Canny(_imgGray, edges, 100, 200, 3);
	//contour
	vector<vector<Point>> contours;
	vector<Vec4i> hierarchy;
	findContours(edges, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));
	//mới

	int w_threshold = 190;
	int h_threshold = 140;
	vector<int> selected;
	Mat drawing = Mat::zeros(edges.size(), CV_8UC3);
	Rect R;
	for (int i = 0; i < contours.size(); i++)
	{
		Scalar color = Scalar(0, 255, 0);
		R = boundingRect(contours[i]);
		// filter contours according to their bounding box
		/*if (R.width > w_threshold && R.height > h_threshold)
		{
			selected.push_back(i);
			drawContours(drawing, contours, i, color, 2, 8, hierarchy, 0, Point());
		}*/
		if (R.width / (double)R.height>1.20 && R.width / (double)R.height < 1.48 && R.width > 200 && R.height > 100)
		{
			selected.push_back(i);
			drawContours(drawing, contours, i, color, 2, 8, hierarchy, 0, Point());
		}
	}
	//filter contour

	/// show image
	cv::imshow("Goc", _img);        // show ảnh gốc
	for (size_t i = 0; i < selected.size(); i++)
	{
		rectangle(_img, boundingRect(contours[selected[i]]), Scalar(0, 0, 255), 5);
	}
	
	cv::imshow("Xam", _imgGray);		// show ảnh xám
	cv::imshow("edges", edges);		// show ảnh Canny
	cv::imshow("contours", drawing);
	cv::imshow("detect", _img);        // show ảnh xám
	cv::waitKey(0);
	return(0);
}