问题描述
拍摄或者扫描图像不是规则的矩形,会对后期处理产生不 好影响,需要通过透视变换校正得到正确形状。
解决思路
通过二值分割 + 形态学方法 + Hough直线 +透视变换
#include#include #include using namespace cv; using namespace std; int main(int argc, char** argv) { Mat src = imread("D:/case6.png"); if (src.empty()) { printf("could not load image...\n"); return 0; } namedWindow("input image", CV_WINDOW_AUTOSIZE); imshow("input image", src); // 二值处理 取反 Mat gray_src, binary, dst; cvtColor(src, gray_src, COLOR_BGR2GRAY); threshold(gray_src, binary, 0, 255, THRESH_BINARY_INV | THRESH_OTSU); //imshow("binary image", binary); // 形态学操作 Mat kernel = getStructuringElement(MORPH_RECT, Size(5, 5), Point(-1, -1)); morphologyEx(binary, dst, MORPH_CLOSE, kernel, Point(-1, -1), 3); //imshow("morphology", dst); // 轮廓发现 bitwise_not(dst, dst, Mat()); vector > contours; vector hireachy; findContours(dst, contours, hireachy, CV_RETR_TREE, CHAIN_APPROX_SIMPLE, Point()); // 轮廓绘t制 int width = src.cols; int height = src.rows; Mat drawImage = Mat::zeros(src.size(), CV_8UC3); for (size_t t = 0; t < contours.size(); t++) { Rect rect = boundingRect(contours[t]); if (rect.width > width / 2 && rect.width < width - 5) { drawContours(drawImage, contours, static_cast<int>(t), Scalar(0, 0, 255), 2, 8, hireachy, 0, Point()); } } //imshow("contours", drawImage); vector lines; Mat contoursImg; int accu = min(width*0.5, height*0.5); cvtColor(drawImage, contoursImg, COLOR_BGR2GRAY); HoughLinesP(contoursImg, lines, CV_HOUGH_PROBABILISTIC, CV_PI / 200.0, accu, accu, 0); Mat linesImage = Mat::zeros(src.size(), CV_8UC3); for (size_t t = 0; t < lines.size(); t++) { Vec4i ln = lines[t]; line(linesImage, Point(ln[0], ln[1]), Point(ln[2], ln[3]), Scalar(0, 0, 255), 2, 8, 0); } printf("number of lines : %d\n", lines.size()); //imshow("lines image", linesImage); // 寻找与定位上下左右四条直线 int deltah = 0; Vec4i topLine, bottomLine; Vec4i leftLine, rightLine; for (int i = 0; i < lines.size(); i++) { Vec4i ln = lines[i]; deltah = abs(ln[3] - ln[1]); if (ln[3] < height / 2.0 && ln[1] < height / 2.0 && deltah < accu - 1) { if (topLine[3] > ln[3] && topLine[3] > 0) { topLine = lines[i]; } else { topLine = lines[i]; } } if (ln[3] > height / 2.0 && ln[1] > height / 2.0 && deltah < accu - 1) { bottomLine = lines[i]; } if (ln[0] < width / 2.0 && ln[2] < width / 2.0) { leftLine = lines[i]; } if (ln[0] > width / 2.0 && ln[2] > width / 2.0) { rightLine = lines[i]; } } cout << "top line : p1(x, y) = " << topLine[0] << "," << topLine[1] << " p2(x, y) = " << topLine[2] << "," << topLine[3] << endl; cout << "bottom line : p1(x, y) = " << bottomLine[0] << "," << bottomLine[1] << " p2(x, y) = " << bottomLine[2] << "," << bottomLine[3] << endl; cout << "left line : p1(x, y) = " << leftLine[0] << "," << leftLine[1] << " p2(x, y) = " << leftLine[2] << "," << leftLine[3] << endl; cout << "right line : p1(x, y) = " << rightLine[0] << "," << rightLine[1] << " p2(x, y) = " << rightLine[2] << "," << rightLine[3] << endl; // 拟合四条直线方程,求直线相交的点 float k1, c1; k1 = float(topLine[3] - topLine[1]) / float(topLine[2] - topLine[0]); c1 = topLine[1] - k1 * topLine[0]; float k2, c2; k2 = float(bottomLine[3] - bottomLine[1]) / float(bottomLine[2] - bottomLine[0]); c2 = bottomLine[1] - k2 * bottomLine[0]; float k3, c3; k3 = float(leftLine[3] - leftLine[1]) / float(leftLine[2] - leftLine[0]); c3 = leftLine[1] - k3 * leftLine[0]; float k4, c4; k4 = float(rightLine[3] - rightLine[1]) / float(rightLine[2] - rightLine[0]); c4 = rightLine[1] - k4 * rightLine[0]; // 四条直线交点 Point p1; // 左上角 p1.x = static_cast<int>((c1 - c3) / (k3 - k1)); p1.y = static_cast<int>(k1*p1.x + c1); Point p2; // 右上角 p2.x = static_cast<int>((c1 - c4) / (k4 - k1)); p2.y = static_cast<int>(k1*p2.x + c1); Point p3; // 左下角 p3.x = static_cast<int>((c2 - c3) / (k3 - k2)); p3.y = static_cast<int>(k2*p3.x + c2); Point p4; // 右下角 p4.x = static_cast<int>((c2 - c4) / (k4 - k2)); p4.y = static_cast<int>(k2*p4.x + c2); cout << "p1(x, y)=" << p1.x << "," << p1.y << endl; cout << "p2(x, y)=" << p2.x << "," << p2.y << endl; cout << "p3(x, y)=" << p3.x << "," << p3.y << endl; cout << "p4(x, y)=" << p4.x << "," << p4.y << endl; // 显示四个点坐标 circle(linesImage, p1, 2, Scalar(255, 0, 0), 2, 8, 0); circle(linesImage, p2, 2, Scalar(255, 0, 0), 2, 8, 0); circle(linesImage, p3, 2, Scalar(255, 0, 0), 2, 8, 0); circle(linesImage, p4, 2, Scalar(255, 0, 0), 2, 8, 0); line(linesImage, Point(topLine[0], topLine[1]), Point(topLine[2], topLine[3]), Scalar(0, 255, 0), 2, 8, 0); //imshow("four corners", linesImage); // 透视变换 vector src_corners(4); src_corners[0] = p1; src_corners[1] = p2; src_corners[2] = p3; src_corners[3] = p4; vector dst_corners(4); dst_corners[0] = Point(0, 0); dst_corners[1] = Point(width, 0); dst_corners[2] = Point(0, height); dst_corners[3] = Point(width, height); // 获取透视变换矩阵 Mat resultImage; Mat warpmatrix = getPerspectiveTransform(src_corners, dst_corners); warpPerspective(src, resultImage, warpmatrix, resultImage.size(), INTER_LINEAR); namedWindow("Final Result", CV_WINDOW_AUTOSIZE); imshow("Final Result", resultImage); waitKey(0); return 0; }