#include<opencv2/opencv.hpp>
#include<iostream>
#include<cmath>
using namespace std;
using namespace cv;
const char input[] = "Input image";
const char output[] = "Output image";
void fileCutLine(int, void*);//对图片边缘切取
void rotateImage(int,void*);//对于图片进行旋转矫正
Mat src, dst,rotateSrc;
int main(void) {
	src = imread("..\\cutLineTest.jpg");
	rotateSrc = imread("..\\rotateTestImage.jpg");
	if (src.empty()||rotateSrc.empty()) {
		cout << "Loading image failed!" << endl;
		return -1;
	}
	pyrDown(rotateSrc, rotateSrc);
	namedWindow(input, WINDOW_AUTOSIZE);
	namedWindow(output, WINDOW_AUTOSIZE);
	int thresh = 134;
	//createTrackbar("Control threshold", output, &thresh, 255, fileCutLine);
	//fileCutLine(thresh, 0);
	createTrackbar("Rotate fix", output, &thresh, 255, rotateImage);
	rotateImage(thresh, 0);
	//imshow(input, src);
	imshow(input, rotateSrc);
	waitKey(0);
	return 0;
}
void fileCutLine(int thresh, void*) {
	Mat gray;
	Mat border;
	Mat kernel = Mat(Size(3, 3), CV_8UC1);
	cvtColor(src, gray, COLOR_BGR2GRAY);
	GaussianBlur(gray, gray, Size(7, 7), 0);
	//高斯模糊降噪
	Canny(gray, border, thresh, 2 * thresh);
	//通过开操作将黑色边缘上的水映文字去掉
	morphologyEx(border, border, MORPH_OPEN, kernel);
	vector<vector<Point>> contours;
	vector<Vec4i> hierarchy;
	findContours(border, contours,hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE,Point(0,0));
	Rect mask;//最后获得的正确范围的遮罩
	//Mat temp = Mat::zeros(src.size(), CV_8UC3);
	//临时图像承载,用于观察边框
	for (int i = 0; i < contours.size(); i++){
		RotatedRect rect = minAreaRect(contours[i]);
		Point2f corner[4];
		//设置图片尺度条件，进行边缘矩形筛选
		if ((rect.size.width > src.cols*0.75)  &&  rect.size.height>src.rows*0.75) {
			rect.points(corner);
			//cout << "************************" << endl;
			line(border, corner[0], corner[1], Scalar(0, 0, 255),2);
			line(border, corner[1], corner[2], Scalar(0, 0, 255),2);
			line(border, corner[3], corner[2], Scalar(0, 0, 255),2);
			line(border, corner[3], corner[0], Scalar(0, 0, 255),2);
			mask = rect.boundingRect();//返回包含旋转矩形的矩形
		}
	}
	cout << mask.width << ' ' << mask.height << endl;
	cout << src.cols << ' ' << src.rows << endl;
	//imshow("temp", temp);
	dst = src(mask);//比较好用
	imshow(output, border);
	if (!dst.empty()) {
		imshow("Result", dst);
	}
}
//如果图片是倾斜
void rotateImage(int thresh,void*) {
	//Mat gray;
	Mat border;
	Mat kernel = Mat(Size(3, 3), CV_8UC1);
	//cvtColor(rotateSrc, gray, COLOR_BGR2GRAY);
	Canny(rotateSrc, border, thresh, 2 * thresh);
	//通过开操作将黑色边缘上的水映文字去掉
	//morphologyEx(border, border, MORPH_OPEN, kernel);
	vector<vector<Point>> contours;
	vector<Vec4i> hierarchy;
	findContours(border, contours, hierarchy, RETR_EXTERNAL, CHAIN_APPROX_SIMPLE, Point(0, 0));
	double angle = 0;//需要记录角度
	Point2f center=Point2f(rotateSrc.rows/2,rotateSrc.cols/2);
	Size fixSize;
	Rect mask;
	Mat temp = Mat(rotateSrc.size(),CV_8UC3);
	for (int i = 0; i < contours.size(); i++){
		RotatedRect rect = minAreaRect(contours[i]);
		//center = rect.center;
		Point2f corner[4];
		rect.points(corner);
		for (int j = 0; j < 4; j++)	{
			line(temp, corner[j], corner[(j + 1) % 4], Scalar(255,255,255), 2);
		}
		if (rect.angle != 0) {
			angle = rect.angle;
			cout << "Angle:" << angle << endl;
		}	
	}
	Mat martix = getRotationMatrix2D(center, angle, 1);//得到仿射矩阵
	warpAffine(rotateSrc, dst, martix, rotateSrc.size());
	imshow("result", dst);
	imshow(output,border);
}

 

在调整阈值时加了traceBar,调的时候方便一些。　　

结果如下（图是百度上随便找的）：