Opencv Rect只创建一个矩形 [英] Opencv Rect only creating one rectangle

问题描述

在我尝试实现粒子滤波器时，我首先在我的图像（红色）中在汽车周围手动绘制了一个矩形（x，y，w，h），然后我获取了50个粒子， x = x + noise（0,15）and y = y + noise（0,15）。

In my attempt to implement particle filter, I have first manually drawn a rectangle(x,y,w,h) around the car in my image (in red color), then i took 50 particles, and assigned them noise i.e x=x+noise(0,15) and y=y+noise(0,15).

然后我想把每个粒子的所有矩形

Then i wanted to dram all the rectangles for each particle in green color, but instead of showing 50 rectangles, it is only showing one rectangle.

#include<opencv2\core\core.hpp>
#include<opencv2\imgproc\imgproc.hpp>
#include<opencv2\highgui\highgui.hpp>

#include<stdio.h>
#include<iostream>
#include<random>

using namespace cv;
using namespace std;



const int N = 50;// no of particles

string intToString(int number){

    //this function has a number input and string output
    std::stringstream ss;
    ss << number;
    return ss.str();
}



int main()
{


    Mat frame;
    frame = imread("f (1).png");
    namedWindow("Out");


    //locating the car manually
    Rect car(175, 210, 42, 31);


    //making a rectangle around the car
    rectangle(frame, car, Scalar(0, 0,255), 1, 8, 0);



    //getting tht height and width of the frame
    const int FRAME_HEIGHT = frame.rows;
    const int FRAME_WIDTH = frame.cols;


    //Particle filter initialization

    Mat Init = (Mat_<float>(4, 1) << car.x, car.y, 0, 0);


    //for a gaussian noise distribution
    std::default_random_engine generator;
    std::normal_distribution<double> distribution(0, 15);


    //Initializing the particles
    std::vector<cv::Mat> particle(N, cv::Mat(4, 1, CV_32F));


    cout << car.x << " " << car.y << "\n";

    for (int i = 0; i < N; i++)
    {
        particle[i].at<float>(0, 0) = Init.at<float>(0, 0) + distribution(generator);
        particle[i].at<float>(1, 0) = Init.at<float>(1, 0) + distribution(generator);
        particle[i].at<float>(2, 0) = 0.0;
        particle[i].at<float>(3, 0) = 0.0;
        cout << particle[i] << "\n";
    }

    for (int i = 0; i < N; i++)
    {
        int x = particle[i].at<float>(0, 0);
        int y = particle[i].at<float>(1, 0);

        rectangle(frame, Rect(x, y, 42, 31), Scalar(0, 255, 0), 1, 8, 0);
    }

    imshow("Out", frame);


    waitKey();





    return 0;
}

输出如下

>

粒子xy坐标在以下图像中，第一个条目是手动硬编码的汽车，其余的都是粒子坐标。

The particle x y coordinates are in the following image, The first entry is of the the car that was manually hard coded, rest all are the particle coordinates.

推荐答案

不幸的是，问题可能在向量初始化。在行中：

Unfortunately, the problem might be in vector initialization. In the line:

 //Initializing the particles
    std::vector<cv::Mat> particle(N, cv::Mat(4, 1, CV_32F));

你所做的是创建N Mat对象，初始化为float类型的1。所以这似乎是好吧...等等！ 如果矢量中的所有Mat对象共享相同的矩阵数据，该怎么办？我们都知道Mat容器有一个头和数据。当标题分配给彼此或复制构造函数被执行时，不复制数据。像我们的情况。什么确切让我们想象一下向量构造函数可能如何工作：

What you do is to create N Mat objects initialized to size 4 by 1 of type float. So this seems to be okay...Wait! What if all Mat objects in the vector share the same matrix data? We all know that Mat container has a header and data. Data is not copied when the headers are assigned to each other or copy constructor is executed. Like in our case. What exactly Let's imagine how the vector constructor might work:

template<class T>
vector::vector (size_type n, const value_type& val = value_type(),
                 const allocator_type& alloc = allocator_type()) {
    // how it can be written? Probably in the following way:
    this->resize(n); // allocates using allocator
    for(int i=0;i<n;i++)
         this->innerBuffer[i] = alloc(val); // runs copy constructor with argument val
                    // in our case, this is cv::Mat(const cv::Mat &)
}

如果你考虑复制cv :: Mat容器，只复制头。如果你想克隆数据本身，你必须直接指定它，例如。使用Mat :: clone（）方法。和向量构造函数绝对不使用clone（）。所以数据没有克隆，所有的Mat对象共享相同的数据，虽然标题是不同的！

And if you think about copying of cv::Mat container, only header is copied. If you would like to clone the data itself, you have to specify it directly, e.g. using Mat::clone() method. And vector constructor definitely does not use clone(). So the data is not cloned and all Mat objects share the same data, although headers are different!

你可以很容易地检查这是否真的不是）：更改代码片段：

You can easy check if this is true (I would be surprised if it wasn't): Change the fragment of code from:

 for (int i = 0; i < N; i++)
    {
        particle[i].at<float>(0, 0) = Init.at<float>(0, 0) + distribution(generator);
        particle[i].at<float>(1, 0) = Init.at<float>(1, 0) + distribution(generator);
        particle[i].at<float>(2, 0) = 0.0;
        particle[i].at<float>(3, 0) = 0.0;
        cout << particle[i] << "\n"; // it is obvius that HERE particles are different
                 // beacuse in the next loop run you overwrite them!
    }

    for (int i = 0; i < N; i++)
    {
        int x = particle[i].at<float>(0, 0);
        int y = particle[i].at<float>(1, 0);

        rectangle(frame, Rect(x, y, 42, 31), Scalar(0, 255, 0), 1, 8, 0);
    }

到

 for (int i = 0; i < N; i++)
    {
        particle[i].at<float>(0, 0) = Init.at<float>(0, 0) + distribution(generator);
        particle[i].at<float>(1, 0) = Init.at<float>(1, 0) + distribution(generator);
        particle[i].at<float>(2, 0) = 0.0;
        particle[i].at<float>(3, 0) = 0.0;

    }

    for (int i = 0; i < N; i++)
    {
        cout << particle[i] << "\n";

        int x = particle[i].at<float>(0, 0);
        int y = particle[i].at<float>(1, 0);

        rectangle(frame, Rect(x, y, 42, 31), Scalar(0, 255, 0), 1, 8, 0);
    }

我希望所有的粒子都是一样的。

I expect that all particles are the same.

参考：（ here ）

 vector(size_type __n, const value_type& __value,
00199          const allocator_type& __a = allocator_type())
00200       : _Base(__n, __a)
00201       { this->_M_impl._M_finish = std::uninitialized_fill_n(this->
00202                                 _M_impl._M_start,
00203                                 __n, __value); }
00204 

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