init - 初始化项目
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Lee Nony
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import java.util.ArrayList;
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import java.util.List;
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import org.opencv.core.Core;
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import org.opencv.core.CvType;
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import org.opencv.core.Mat;
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import org.opencv.core.MatOfPoint;
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import org.opencv.core.Point;
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import org.opencv.core.Scalar;
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import org.opencv.highgui.HighGui;
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import org.opencv.imgcodecs.Imgcodecs;
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import org.opencv.imgproc.Imgproc;
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//This program demonstrates how to use OpenCV PCA to extract the orientation of an object.
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class IntroductionToPCA {
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private void drawAxis(Mat img, Point p_, Point q_, Scalar colour, float scale) {
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Point p = new Point(p_.x, p_.y);
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Point q = new Point(q_.x, q_.y);
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//! [visualization1]
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double angle = Math.atan2(p.y - q.y, p.x - q.x); // angle in radians
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double hypotenuse = Math.sqrt((p.y - q.y) * (p.y - q.y) + (p.x - q.x) * (p.x - q.x));
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// Here we lengthen the arrow by a factor of scale
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q.x = (int) (p.x - scale * hypotenuse * Math.cos(angle));
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q.y = (int) (p.y - scale * hypotenuse * Math.sin(angle));
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Imgproc.line(img, p, q, colour, 1, Imgproc.LINE_AA, 0);
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// create the arrow hooks
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p.x = (int) (q.x + 9 * Math.cos(angle + Math.PI / 4));
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p.y = (int) (q.y + 9 * Math.sin(angle + Math.PI / 4));
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Imgproc.line(img, p, q, colour, 1, Imgproc.LINE_AA, 0);
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p.x = (int) (q.x + 9 * Math.cos(angle - Math.PI / 4));
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p.y = (int) (q.y + 9 * Math.sin(angle - Math.PI / 4));
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Imgproc.line(img, p, q, colour, 1, Imgproc.LINE_AA, 0);
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//! [visualization1]
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}
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private double getOrientation(MatOfPoint ptsMat, Mat img) {
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List<Point> pts = ptsMat.toList();
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//! [pca]
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// Construct a buffer used by the pca analysis
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int sz = pts.size();
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Mat dataPts = new Mat(sz, 2, CvType.CV_64F);
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double[] dataPtsData = new double[(int) (dataPts.total() * dataPts.channels())];
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for (int i = 0; i < dataPts.rows(); i++) {
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dataPtsData[i * dataPts.cols()] = pts.get(i).x;
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dataPtsData[i * dataPts.cols() + 1] = pts.get(i).y;
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}
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dataPts.put(0, 0, dataPtsData);
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// Perform PCA analysis
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Mat mean = new Mat();
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Mat eigenvectors = new Mat();
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Mat eigenvalues = new Mat();
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Core.PCACompute2(dataPts, mean, eigenvectors, eigenvalues);
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double[] meanData = new double[(int) (mean.total() * mean.channels())];
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mean.get(0, 0, meanData);
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// Store the center of the object
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Point cntr = new Point(meanData[0], meanData[1]);
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// Store the eigenvalues and eigenvectors
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double[] eigenvectorsData = new double[(int) (eigenvectors.total() * eigenvectors.channels())];
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double[] eigenvaluesData = new double[(int) (eigenvalues.total() * eigenvalues.channels())];
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eigenvectors.get(0, 0, eigenvectorsData);
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eigenvalues.get(0, 0, eigenvaluesData);
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//! [pca]
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//! [visualization]
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// Draw the principal components
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Imgproc.circle(img, cntr, 3, new Scalar(255, 0, 255), 2);
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Point p1 = new Point(cntr.x + 0.02 * eigenvectorsData[0] * eigenvaluesData[0],
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cntr.y + 0.02 * eigenvectorsData[1] * eigenvaluesData[0]);
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Point p2 = new Point(cntr.x - 0.02 * eigenvectorsData[2] * eigenvaluesData[1],
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cntr.y - 0.02 * eigenvectorsData[3] * eigenvaluesData[1]);
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drawAxis(img, cntr, p1, new Scalar(0, 255, 0), 1);
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drawAxis(img, cntr, p2, new Scalar(255, 255, 0), 5);
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double angle = Math.atan2(eigenvectorsData[1], eigenvectorsData[0]); // orientation in radians
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//! [visualization]
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return angle;
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}
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public void run(String[] args) {
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//! [pre-process]
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// Load image
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String filename = args.length > 0 ? args[0] : "../data/pca_test1.jpg";
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Mat src = Imgcodecs.imread(filename);
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// Check if image is loaded successfully
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if (src.empty()) {
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System.err.println("Cannot read image: " + filename);
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System.exit(0);
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}
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Mat srcOriginal = src.clone();
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HighGui.imshow("src", srcOriginal);
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// Convert image to grayscale
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Mat gray = new Mat();
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Imgproc.cvtColor(src, gray, Imgproc.COLOR_BGR2GRAY);
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// Convert image to binary
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Mat bw = new Mat();
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Imgproc.threshold(gray, bw, 50, 255, Imgproc.THRESH_BINARY | Imgproc.THRESH_OTSU);
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//! [pre-process]
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//! [contours]
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// Find all the contours in the thresholded image
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List<MatOfPoint> contours = new ArrayList<>();
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Mat hierarchy = new Mat();
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Imgproc.findContours(bw, contours, hierarchy, Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_NONE);
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for (int i = 0; i < contours.size(); i++) {
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// Calculate the area of each contour
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double area = Imgproc.contourArea(contours.get(i));
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// Ignore contours that are too small or too large
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if (area < 1e2 || 1e5 < area)
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continue;
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// Draw each contour only for visualisation purposes
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Imgproc.drawContours(src, contours, i, new Scalar(0, 0, 255), 2);
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// Find the orientation of each shape
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getOrientation(contours.get(i), src);
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}
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//! [contours]
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HighGui.imshow("output", src);
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HighGui.waitKey();
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System.exit(0);
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}
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}
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public class IntroductionToPCADemo {
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public static void main(String[] args) {
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// Load the native OpenCV library
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System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
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new IntroductionToPCA().run(args);
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}
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}
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