java - 为什么 cvFindContours() 方法不能在 javacv 中正确检测轮廓？

Question

我在 StackOverflow 中解决了许多问题，并且能够开发小程序来正确检测正方形和矩形。这是我的示例代码

public static CvSeq findSquares(final IplImage src, CvMemStorage storage) {
    CvSeq squares = new CvContour();
    squares = cvCreateSeq(0, sizeof(CvContour.class), sizeof(CvSeq.class), storage);
    IplImage pyr = null, timg = null, gray = null, tgray;
    timg = cvCloneImage(src);
    CvSize sz = cvSize(src.width(), src.height());
    tgray = cvCreateImage(sz, src.depth(), 1);
    gray = cvCreateImage(sz, src.depth(), 1);
    // cvCvtColor(gray, src, 1);
    pyr = cvCreateImage(cvSize(sz.width() / 2, sz.height() / 2), src.depth(), src.nChannels());
    // down-scale and upscale the image to filter out the noise
    // cvPyrDown(timg, pyr, CV_GAUSSIAN_5x5);
    // cvPyrUp(pyr, timg, CV_GAUSSIAN_5x5);
    // cvSaveImage("ha.jpg",timg);
    CvSeq contours = new CvContour();
    // request closing of the application when the image window is closed
    // show image on window
    // find squares in every color plane of the image
    for (int c = 0; c < 3; c++) {
        IplImage channels[] = { cvCreateImage(sz, 8, 1), cvCreateImage(sz, 8, 1), cvCreateImage(sz, 8, 1) };
        channels[c] = cvCreateImage(sz, 8, 1);
        if (src.nChannels() > 1) {
            cvSplit(timg, channels[0], channels[1], channels[2], null);
        } else {
            tgray = cvCloneImage(timg);
        }
        tgray = channels[c];
        // // try several threshold levels
        for (int l = 0; l < N; l++) {
            // hack: use Canny instead of zero threshold level.
            // Canny helps to catch squares with gradient shading
            if (l == 0) {
                // apply Canny. Take the upper threshold from slider
                // and set the lower to 0 (which forces edges merging)
                cvCanny(tgray, gray, 0, thresh, 5);
                // dilate canny output to remove potential
                // // holes between edge segments
                cvDilate(gray, gray, null, 1);
            } else {
                // apply threshold if l!=0:
                cvThreshold(tgray, gray, (l + 1) * 255 / N, 255,
                        CV_THRESH_BINARY);
            }
            // find contours and store them all as a list
            cvFindContours(gray, storage, contours, sizeof(CvContour.class), CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);
            CvSeq approx;
            // test each contour
            while (contours != null && !contours.isNull()) {
                if (contours.elem_size() > 0) {
                    approx = cvApproxPoly(contours, Loader.sizeof(CvContour.class), storage, CV_POLY_APPROX_DP, cvContourPerimeter(contours) * 0.02, 0);
                    if (approx.total() == 4 && Math.abs(cvContourArea(approx, CV_WHOLE_SEQ, 0)) > 1000 && cvCheckContourConvexity(approx) != 0) {
                        double maxCosine = 0;
                        for (int j = 2; j < 5; j++) {
                            // find the maximum cosine of the angle between
                            // joint edges
                            double cosine = Math.abs(angle(
                                            new CvPoint(cvGetSeqElem(
                                                    approx, j % 4)),
                                            new CvPoint(cvGetSeqElem(
                                                    approx, j - 2)),
                                            new CvPoint(cvGetSeqElem(
                                                    approx, j - 1))));
                            maxCosine = Math.max(maxCosine, cosine);
                        }
                        if (maxCosine < 0.2) {
                            CvRect x = cvBoundingRect(approx, l);
                            if ((x.width() * x.height()) < 50000) {
                                System.out.println("Width : " + x.width()
                                        + " Height : " + x.height());
                                cvSeqPush(squares, approx);
                            }
                        }
                    }
                }
                contours = contours.h_next();
            }
            contours = new CvContour();
        }
    }
    return squares;
}

我使用这张图片来检测矩形和正方形

我需要识别以下输出

和

但是当我运行上面的代码时，它只检测到以下矩形。但我不知道这是什么原因。请有人解释一下原因。

这是我得到的输出。

请在上面的代码中解释问题并给出一些建议来检测这个正方形和矩形。

Answer 1

给定一个掩码图像(二进制图像，如您的第二个图)，cvFindContours() 为您提供轮廓(几个点列表)。
看这个链接:http://dasl.mem.drexel.edu/~noahKuntz/openCVTut7.html