问使用OpenCV和Java实现自动透视校正

EN

public static void correctPerspective() {

    String fileName = "IMG_20141024_132131.jpg";
    Mat imgSource = Highgui.imread(fileName, Highgui.CV_LOAD_IMAGE_UNCHANGED);
    // convert the image to black and white does (8 bit)
    Imgproc.Canny(imgSource.clone(), imgSource, 50, 50);

    // apply gaussian blur to smoothen lines of dots
    Imgproc.GaussianBlur(imgSource, imgSource, new org.opencv.core.Size(5, 5), 5);

    // find the contours
    List<MatOfPoint> contours = new ArrayList<MatOfPoint>();
    Imgproc.findContours(imgSource, contours, new Mat(), Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE);

    double maxArea = -1;
    MatOfPoint temp_contour = contours.get(0); // the largest is at the
                                                // index 0 for starting
                                                // point
    MatOfPoint2f approxCurve = new MatOfPoint2f();

    for (int idx = 0; idx < contours.size(); idx++) {
        temp_contour = contours.get(idx);
        double contourarea = Imgproc.contourArea(temp_contour);
        // compare this contour to the previous largest contour found
        if (contourarea > maxArea) {
            // check if this contour is a square
            MatOfPoint2f new_mat = new MatOfPoint2f(temp_contour.toArray());
            int contourSize = (int) temp_contour.total();
            MatOfPoint2f approxCurve_temp = new MatOfPoint2f();
            Imgproc.approxPolyDP(new_mat, approxCurve_temp, contourSize * 0.05, true);
            if (approxCurve_temp.total() == 4) {
                maxArea = contourarea;
                approxCurve = approxCurve_temp;
            }
        }
    }

    Imgproc.cvtColor(imgSource, imgSource, Imgproc.COLOR_BayerBG2RGB);
    Mat sourceImage = Highgui.imread(fileName, Highgui.CV_LOAD_IMAGE_UNCHANGED);
    double[] temp_double;
    temp_double = approxCurve.get(0, 0);
    Point p1 = new Point(temp_double[0], temp_double[1]);
    // Core.circle(imgSource,p1,55,new Scalar(0,0,255));
    // Imgproc.warpAffine(sourceImage, dummy, rotImage,sourceImage.size());
    temp_double = approxCurve.get(1, 0);
    Point p2 = new Point(temp_double[0], temp_double[1]);
    // Core.circle(imgSource,p2,150,new Scalar(255,255,255));
    temp_double = approxCurve.get(2, 0);
    Point p3 = new Point(temp_double[0], temp_double[1]);
    // Core.circle(imgSource,p3,200,new Scalar(255,0,0));
    temp_double = approxCurve.get(3, 0);
    Point p4 = new Point(temp_double[0], temp_double[1]);
    // Core.circle(imgSource,p4,100,new Scalar(0,0,255));
    List<Point> source = new ArrayList<Point>();
    source.add(p1);
    source.add(p2);
    source.add(p3);
    source.add(p4);
    Mat startM = Converters.vector_Point2f_to_Mat(source);
    Mat result = warp(sourceImage, startM);

    Highgui.imwrite("corrected.jpg", result);
}

public static Mat warp(Mat inputMat, Mat startM) {

    int resultWidth = 1200;
    int resultHeight = 680;

    Point ocvPOut4 = new Point(0, 0);
    Point ocvPOut1 = new Point(0, resultHeight);
    Point ocvPOut2 = new Point(resultWidth, resultHeight);
    Point ocvPOut3 = new Point(resultWidth, 0);

    if (inputMat.height() > inputMat.width()) {
        // int temp = resultWidth;
        // resultWidth = resultHeight;
        // resultHeight = temp;

        ocvPOut3 = new Point(0, 0);
        ocvPOut4 = new Point(0, resultHeight);
        ocvPOut1 = new Point(resultWidth, resultHeight);
        ocvPOut2 = new Point(resultWidth, 0);
    }

    Mat outputMat = new Mat(resultWidth, resultHeight, CvType.CV_8UC4);

    List<Point> dest = new ArrayList<Point>();
    dest.add(ocvPOut1);
    dest.add(ocvPOut2);
    dest.add(ocvPOut3);
    dest.add(ocvPOut4);

    Mat endM = Converters.vector_Point2f_to_Mat(dest);

    Mat perspectiveTransform = Imgproc.getPerspectiveTransform(startM, endM);

    Imgproc.warpPerspective(inputMat, outputMat, perspectiveTransform, new Size(resultWidth, resultHeight), Imgproc.INTER_CUBIC);

    return outputMat;
}