OpenCV：将点旋转一个角度：Offset/shift in solution

Question

我正在尝试按用户定义的角度旋转矢量中的一组点，并在 SO 处找到了解决方案。在以下代码中，输出图像的尺寸和旋转角度（45 度）是正确的，但点的位置似乎发生了偏移。有人可以给我提示，问题是什么？编辑：查看生成的线正确旋转的附加图片，但结果不是从 (0,0)（左上角）开始。

generated Line rotated Line

cv::Point rotate2d(const cv::Point& inPoint, const double& angRad)
{
    cv::Point outPoint;
    //CW rotation
    outPoint.x = std::cos(angRad)*inPoint.x - std::sin(angRad)*inPoint.y;
    outPoint.y = std::sin(angRad)*inPoint.x + std::cos(angRad)*inPoint.y;
    return outPoint;
}

cv::Point rotatePoint(const cv::Point& inPoint, const cv::Point& center, const double& angRad)
{
    return rotate2d(inPoint - center, angRad) + center;
}


int main( int, char** argv )
{
    // Create an dark Image with a gray line in the middle
    Mat img = Mat(83, 500, CV_8U);
    img = Scalar(0);
    vector<Point> pointsModel;

    for ( int i = 0; i<500; i++)
    {
        pointsModel.push_back(Point(i , 41));
    }

    for ( int i=0; i<pointsModel.size(); i++)
    {
        circle(img, pointsModel[i], 1, Scalar(120,120,120), 1, LINE_8, 0);
    }
    imshow("Points", img);

    // Rotate Points
    vector<Point> rotatedPoints;
    Point tmpPoint;
    cv::Point pt( img.cols/2.0, img.rows/2.0 );
    for ( int i=0; i<pointsModel.size(); i++)
    {
        tmpPoint = rotatePoint(pointsModel[i] , pt , 0.7854);
        rotatedPoints.push_back(tmpPoint);
    }
    Rect bb = boundingRect(rotatedPoints);
    cout << bb;
    Mat rotatedImg = Mat(bb.height, bb.width, img.type());
    rotatedImg = Scalar(0);

    for (int i=0; i<rotatedPoints.size(); i++ )
    {
        circle(rotatedImg, rotatedPoints[i], 1, Scalar(120,120,120), 1, LINE_8, 0);
    }
    imshow("Points Rotated", rotatedImg);
    waitKey();

    return 0;
}

Answer 1

这两行：

Rect bb = boundingRect(rotatedPoints);
Mat rotatedImg = Mat(bb.height, bb.width, img.type());

您将新图像尺寸设置为 bb 的大小。但是 bb 本身有一个平移偏移量，您在继续转换点时没有考虑到它；所以等效地，新的 viewport 本身是偏移的。

您可以做的是扩展原始图像以适应 bb，即像这样：

Mat rotatedImg(std::max(img.width(), bb.x + bb.width), std::max(img.height(), bb.y + bb.height), img.type());

OpenCV：将点旋转一个角度：Offset/shift in solution

OpenCV: Rotate points by an angle: Offset/shift in solution

c++

opencv

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points