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authorbsdnoobz <nash@bsd-noobz.com>2013-01-12 14:58:51 +0700
committerbsdnoobz <nash@bsd-noobz.com>2013-01-12 14:58:51 +0700
commitb2de783a4a03ee42e66dfe1c994ba7e3bf44c8de (patch)
treeb03cabaca7a847fb0fb9735a38f0e412de92cf0a
parent7c7c9a383b44a1de3de3ae866f056da50975f099 (diff)
Added quad-segmentation.cpp
-rw-r--r--quad-segmentation.cpp138
1 files changed, 138 insertions, 0 deletions
diff --git a/quad-segmentation.cpp b/quad-segmentation.cpp
new file mode 100644
index 0000000..bb341cd
--- /dev/null
+++ b/quad-segmentation.cpp
@@ -0,0 +1,138 @@
+/**
+ * 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>
+
+cv::Point2f center(0,0);
+
+cv::Point2f computeIntersect(cv::Vec4i a,
+ cv::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)))
+ {
+ cv::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 cv::Point2f(-1, -1);
+}
+
+void sortCorners(std::vector<cv::Point2f>& corners,
+ cv::Point2f center)
+{
+ std::vector<cv::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]);
+ }
+
+ cv::Point2f tl = top[0].x > top[1].x ? top[1] : top[0];
+ cv::Point2f tr = top[0].x > top[1].x ? top[0] : top[1];
+ cv::Point2f bl = bot[0].x > bot[1].x ? bot[1] : bot[0];
+ cv::Point2f br = bot[0].x > bot[1].x ? bot[0] : bot[1];
+
+ corners.clear();
+ corners.push_back(tl);
+ corners.push_back(tr);
+ corners.push_back(br);
+ corners.push_back(bl);
+}
+
+int main()
+{
+ cv::Mat src = cv::imread("image.jpg");
+ if (src.empty())
+ return -1;
+
+ cv::Mat bw;
+ cv::cvtColor(src, bw, CV_BGR2GRAY);
+ cv::blur(bw, bw, cv::Size(3, 3));
+ cv::Canny(bw, bw, 100, 100, 3);
+
+ std::vector<cv::Vec4i> lines;
+ cv::HoughLinesP(bw, lines, 1, CV_PI/180, 70, 30, 10);
+
+ // Expand the lines
+ for (int i = 0; i < lines.size(); i++)
+ {
+ cv::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];
+ }
+
+ std::vector<cv::Point2f> corners;
+ for (int i = 0; i < lines.size(); i++)
+ {
+ for (int j = i+1; j < lines.size(); j++)
+ {
+ cv::Point2f pt = computeIntersect(lines[i], lines[j]);
+ if (pt.x >= 0 && pt.y >= 0)
+ corners.push_back(pt);
+ }
+ }
+
+ std::vector<cv::Point2f> approx;
+ cv::approxPolyDP(cv::Mat(corners), approx, cv::arcLength(cv::Mat(corners), true) * 0.02, true);
+
+ if (approx.size() != 4)
+ {
+ std::cout << "The object is not quadrilateral!" << std::endl;
+ return -1;
+ }
+
+ // Get mass center
+ for (int i = 0; i < corners.size(); i++)
+ center += corners[i];
+ center *= (1. / corners.size());
+
+ sortCorners(corners, center);
+
+ cv::Mat dst = src.clone();
+
+ // Draw lines
+ for (int i = 0; i < lines.size(); i++)
+ {
+ cv::Vec4i v = lines[i];
+ cv::line(dst, cv::Point(v[0], v[1]), cv::Point(v[2], v[3]), CV_RGB(0,255,0));
+ }
+
+ // Draw corner points
+ cv::circle(dst, corners[0], 3, CV_RGB(255,0,0), 2);
+ cv::circle(dst, corners[1], 3, CV_RGB(0,255,0), 2);
+ cv::circle(dst, corners[2], 3, CV_RGB(0,0,255), 2);
+ cv::circle(dst, corners[3], 3, CV_RGB(255,255,255), 2);
+
+ // Draw mass center
+ cv::circle(dst, center, 3, CV_RGB(255,255,0), 2);
+
+ cv::Mat quad = cv::Mat::zeros(300, 220, CV_8UC3);
+
+ std::vector<cv::Point2f> quad_pts;
+ quad_pts.push_back(cv::Point2f(0, 0));
+ quad_pts.push_back(cv::Point2f(quad.cols, 0));
+ quad_pts.push_back(cv::Point2f(quad.cols, quad.rows));
+ quad_pts.push_back(cv::Point2f(0, quad.rows));
+
+ cv::Mat transmtx = cv::getPerspectiveTransform(corners, quad_pts);
+ cv::warpPerspective(src, quad, transmtx, quad.size());
+
+ cv::imshow("image", dst);
+ cv::imshow("quadrilateral", quad);
+ cv::waitKey();
+ return 0;
+}
+