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| -rw-r--r-- | quad-segmentation.cpp | 138 |
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; +} + |