OpenCV C ++缩放功能

Question

I am using an IP Camera for Human Detection using OpenCV dnn and C++, I need to implement zoom functionality to detect humans from a distance over 10 meters, but I found, performing zoom in a live video using c++ doesn't exist(please correct me, if I am wrong)

我尝试了以下代码来缩放视频

cv::Mat src, dst, tmp;
        tmp = src;
        dst = tmp;
        pyrUp(tmp, dst, cv::Size(tmp.cols * 2, tmp.rows * 2));
        frame.image = dst;

But, Image Pyramids did not zoom my video.

Can you please help me with a zoom function to achieve my objective.

Answer 1

软件缩放通常称为选择图像区域（ROI）。您必须选择一个合适的ROI矩形。

cv::Rect roi(x, y, w, h);
cv::Mat dst = src(roi);

Answer 2

如果要在每个方向上将图像缩小2倍，则可以通过以下方式调用该函数：//指定fx和fy，然后让函数计算目标图像尺寸。

resize(src, dst, Size(), 0.5, 0.5, interpolation);