java - 使用 OpenCV 将代码从 python 移植到 java

Question

我正在尝试获取 python 代码的 java 实现。该代码与opencv相关。 python 代码工作得很好，但我在让它与 java 一起工作时遇到了一些困难，我得到了 null 异常。我不知道它是否与reshape函数或get/put函数有关。

Python:

approx = cv2.approxPolyDP(i,0.02*peri,True)
...
approx=rectify(approx)
...
def rectify(h):
    h = h.reshape((4,2))
    hnew = np.zeros((4,2),dtype = np.float32)

    add = h.sum(1)
    hnew[0] = h[np.argmin(add)]
    hnew[2] = h[np.argmax(add)]

    diff = np.diff(h,axis = 1)
    hnew[1] = h[np.argmin(diff)]
    hnew[3] = h[np.argmax(diff)]

    return hnew

Java:

Imgproc.approxPolyDP(newMtx, approx, 0.02 * peri, true);
...
approx = rectify(approx);
...
private Mat rectify(Mat approx) {

    DoubleMatrix ndApproxNew, ndAdd, ndApprox;
    double [] d;
    Mat hnew;

    ndApproxNew = DoubleMatrix.zeros(4, 2);
    hnew = new Mat();

    approx = approx.reshape(0, 4);

    // sum
    d = approx.get(4, 2);
    Log.d(TAG, "daily - heigth: " + approx.height() + " width: " + approx.width());
    ndApprox = new DoubleMatrix(4, 2, d);

    Log.d(TAG, "daily - " + ndApprox.getRow(0)); // <- ERROR NULL
    Log.d(TAG, "daily - " + ndApprox.getRow(1));
    Log.d(TAG, "daily - " + ndApprox.getRow(2));
    Log.d(TAG, "daily - " + ndApprox.getRow(3));

Answer 1

Mat::reshape 的第一个参数让您指定 Mat 对象的 channel 数。

当您 reshape approx 变量时，您将向其传递零 channel 。您的问题可能出在这一行:

approx = approx.reshape(0, 4);