quadSeg.cpp

/**
 * Automatic perspective correction for quadrilateral objects. See the tutorial at
 * http://opencv-code.com/tutorials/automatic-perspective-correction-for-quadrilateral-objects/
 */
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
#include <stdio.h>

using namespace cv;
using namespace std;

Point2f center(0,0);

Point2f computeIntersect(Vec4i a, Vec4i b)
{
	int x1 = a[0], y1 = a[1], x2 = a[2], y2 = a[3], x3 = b[0], y3 = b[1], x4 = b[2], y4 = b[3];
	float denom;

	if (float d = ((float)(x1 - x2) * (y3 - y4)) - ((y1 - y2) * (x3 - x4)))
	{
		Point2f pt;
		pt.x = ((x1 * y2 - y1 * x2) * (x3 - x4) - (x1 - x2) * (x3 * y4 - y3 * x4)) / d;
		pt.y = ((x1 * y2 - y1 * x2) * (y3 - y4) - (y1 - y2) * (x3 * y4 - y3 * x4)) / d;
		return pt;
	}
	else
		return Point2f(-1, -1);
	}

	void sortCorners(vector<Point2f>& corners, Point2f center)
	{
	vector<Point2f> top, bot;

	for (int i = 0; i < corners.size(); i++)
	{
		if (corners[i].y < center.y)
										top.push_back(corners[i]);
		else
										bot.push_back(corners[i]);
	}
	corners.clear();

	if (top.size() == 2 && bot.size() == 2) {
		Point2f tl = top[0].x > top[1].x ? top[1] : top[0];
		Point2f tr = top[0].x > top[1].x ? top[0] : top[1];
		Point2f bl = bot[0].x > bot[1].x ? bot[1] : bot[0];
		Point2f br = bot[0].x > bot[1].x ? bot[0] : bot[1];


		corners.push_back(tl);
		corners.push_back(tr);
		corners.push_back(br);
		corners.push_back(bl);
	}
}

void onChange(int i, void* v) {;}

int main(int, char**)
{
	Mat src, bw, dst, quad, transmtx;

	VideoCapture cap(0); // open the default camera
	if(!cap.isOpened())  // check if we succeeded
			return -1;

	string win1 = "win1";
	string win2 = "win2";
	namedWindow(win1, CV_WINDOW_NORMAL);
	// namedWindow(win2, CV_WINDOW_NORMAL);

	int rho = 1; // increase rho == increase tolerance of line
	int theta = 1;
	int thresh = 70;
	int minLength = 30;
	int maxGap = 10;

	createTrackbar("rho", win1, &rho, 199, onChange);
	createTrackbar("theta", win1, &theta, 179, onChange);
	createTrackbar("thresh", win1, &thresh, 140, onChange);
	createTrackbar("minLength", win1, &minLength, 60, onChange);
	createTrackbar("maxGap", win1, &maxGap, 20, onChange);

	for(;;)	{
		cap >> src;
		if (src.empty()) {
			cout << "Source is empty" << endl;
			continue;
		}
		src.copyTo(dst);

		cvtColor(src, bw, CV_BGR2GRAY);
		blur(bw, bw, Size(3, 3));
		Canny(bw, bw, 100, 100, 3);

		vector<Vec4i> lines;

		HoughLinesP(bw, lines, ((rho+1)/100.0), CV_PI/180*(theta+1),
								thresh, (minLength), (maxGap));

		// Expand the lines
		for (int i = 0; i < lines.size(); i++)
		{
		 Vec4i v = lines[i];
		 lines[i][0] = 0;
		 lines[i][1] = ((float)v[1] - v[3]) / (v[0] - v[2]) * -v[0] + v[1];
		 lines[i][2] = src.cols;
		 lines[i][3] = ((float)v[1] - v[3]) / (v[0] - v[2]) * (src.cols - v[2]) + v[3];
		}

		vector<Point2f> corners;
		for (int i = 0; i < lines.size(); i++)
		{
		 for (int j = i+1; j < lines.size(); j++)
		 {
		  Point2f pt = computeIntersect(lines[i], lines[j]);
		  if (pt.x >= 0 && pt.y >= 0)
		   corners.push_back(pt);
		 }
		}
		vector<Point2f> approx;

		if (corners.size() >= 4) {
			approxPolyDP(Mat(corners), approx, arcLength(Mat(corners), true) * 0.02, true);

			// if (approx.size() != 4)
			// {
			//  cout << "approx.size == " << approx.size() << endl;
			// }

			// Get mass center
			for (int i = 0; i < corners.size(); i++) center += corners[i];
			center *= (1. / corners.size());

			sortCorners(corners, center);
			if (corners.size() == 0) cout << "Number of corners is 0... skipping" << endl;

			// Draw lines
			for (int i = 0; i < lines.size(); i++)
			{
			 Vec4i v = lines[i];
			 line(dst, Point(v[0], v[1]), Point(v[2], v[3]), CV_RGB(0,255,0));
			}

			// Draw corner points
			circle(dst, corners[0], 3, CV_RGB(255,0,0), 2);
			circle(dst, corners[1], 3, CV_RGB(0,255,0), 2);
			circle(dst, corners[2], 3, CV_RGB(0,0,255), 2);
			circle(dst, corners[3], 3, CV_RGB(255,255,255), 2);
			//
			// Draw mass center
			circle(dst, center, 3, CV_RGB(255,255,0), 2);

			quad = Mat::zeros(300, 220, CV_8UC3);

			vector<Point2f> quad_pts;
			quad_pts.push_back(Point2f(0, 0));
			quad_pts.push_back(Point2f(quad.cols, 0));
			quad_pts.push_back(Point2f(quad.cols, quad.rows));
			quad_pts.push_back(Point2f(0, quad.rows));

		// transmtx = getPerspectiveTransform(corners, quad_pts);
		// warpPerspective(src, quad, transmtx, quad.size());

		}
		imshow(win1, dst);
		// imshow(win2, quad);

    if(waitKey(30) == 'q') break;
		}
		return 0;
	}