OpenCV案例(一)：切边

版权声明：本文为博主原创文章，博主欢迎各位转载。 https://blog.csdn.net/tuwenqi2013/article/details/83592138

实现思路：最大外接矩阵边缘检测+旋转+选取ROI区域裁剪

代码：

#include <iostream>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <math.h>
#include <iostream>

using namespace std;
using namespace cv;

Mat img1, gray, canny_gray, dest;
double threshold_value = 180.0;

void RotateImg(void);
void GetTargetImg(Mat img);

int main(int argc, char * argv[])
{

	img1 = imread("../img/11.png");
	imshow("原始图像", img1);

	RotateImg();         //旋转图片
	GetTargetImg(img1);  //裁剪图片

	if (waitKey() == 27)
		return 0;
}

void RotateImg(void)
{
	Mat canny_output;
	vector<vector<Point>> contours;
	vector<	Vec4i> hireachy;
	Mat drawImg = Mat::zeros(img1.size(), CV_8UC3);

	cvtColor(img1, gray, COLOR_BGR2BGRA);
	Canny(gray, canny_output, threshold_value, threshold_value * 2, 3, false);
	imshow("Canny算子图像", canny_output);

	findContours(canny_output, contours, hireachy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0));
	float maxw = 0;
	float maxh = 0;
	int angle = 0;
	for (int t = 0; t < contours.size(); t++)
	{
		RotatedRect rotate = minAreaRect(contours[t]);
		angle = abs(rotate.angle);
		if (angle > 0)
		{
			maxw = max(maxw, rotate.size.width);
			maxh = max(maxh, rotate.size.height);
		}
	}
	RNG rng(12345);

	for (int t = 0; t < contours.size(); t++)
	{
		RotatedRect rota = minAreaRect(contours[t]);
		if (maxw == rota.size.width && maxh == rota.size.height)
		{
			angle = rota.angle;          //找到合适的旋转角度		
		}
	}
	Point2f center(img1.cols / 2, img1.rows / 2);
	Mat rotaImg = getRotationMatrix2D(center, angle, 1.0);  //找到旋转矩阵

	warpAffine(img1, dest, rotaImg, img1.size(), INTER_LINEAR);
	imshow("摆正后的图像", dest);
}

void GetTargetImg(Mat img)
{
	Mat canny_output;
	vector<vector<Point>> contours;
	vector<	Vec4i> hireachy;
	Mat drawImg = Mat::zeros(dest.size(), CV_8UC3);
	Rect box;
	cvtColor(dest, gray, COLOR_BGR2BGRA);
	Canny(gray, canny_output, threshold_value, threshold_value * 2, 3, false);
	Mat drawImage = Mat::zeros(dest.size(), CV_8UC3);

	findContours(canny_output, contours, hireachy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0));
	int maxw = dest.cols*0.5;
	int maxh = dest.rows*0.5;

	cout << "maxw: " << maxw << "maxh: " << maxh << endl;
	RNG rng(12345);
	int angle = 0;

	for (int t = 0; t < contours.size(); t++)
	{
		RotatedRect rota = minAreaRect(contours[t]);
		float  angle = abs(rota.angle);
		cout << "angle：" << angle << endl;
		if (maxw < rota.size.width && maxh < rota.size.height)
		{
			cout << "最小外包矩形：" << box << endl;			
			box = rota.boundingRect();	           //找到裁剪矩阵				
		}
	}

	if (box.width > 0 && box.height > 0)
	{
		Mat roiimg = dest(box);
		imshow("结果图像", roiimg);          //显示裁剪后的图像
		imwrite("1.1.jpg",roiimg);           //保存图片
	}
}

原始图片：

摆正后的图片：

最后的处理结果：