OpenCV基础篇之画图及RNG随机数对象

时间：2022-02-17 20:45:31

程序及分析

/*

 * FileName : random_gen.c

 * Author   : xiahouzuoxin @163.com

 * Version  : v1.0

 * Date     : Tue 29 Jul 2014 08:31:41 PM CST

 * Brief    :

 *

 * Copyright (C) MICL,USTB

 */

#include <cv.h>

#include <highgui.h>

#include <iostream>

using namespace std;

using namespace cv;

const char wndname[] = "Drawing";

const int RAND_N = 100;

void help(void)

{

    cout<<"Usage:./drawing"<<endl;

}

static Scalar random_color(RNG& rng)

{

    int icolor = (unsigned)rng;

    return Scalar(icolor&0xFF, (icolor>>8)&0xFF, (icolor>>16)&0xFF);

}

int main(int argc, char *argv[])

{

    int line_type = CV_AA;

    int i = 0;

    int width = 1000;

    int height = 700;

    int x1 = -width/2;

    int x2 = width*3/2;

    int y1 = -height/2;

    int y2 = height*3/2;

    const int DELAY = 10;

    RNG rng(0xFFFFFFFF);

    Mat image = Mat::zeros(height, width, CV_8UC3);

    imshow(wndname, image);

    waitKey(DELAY);

    for (i=0; i<RAND_N; i++) {

        Point pt1;

        Point pt2;

        pt1.x = rng.uniform(x1, x2);

        pt1.y = rng.uniform(y1, y2);

        pt2.x = rng.uniform(x1, x2);

        pt2.y = rng.uniform(y1, y2);

        line(image, pt1, pt2, random_color(rng), rng.uniform(1,5), line_type);

    }

    imshow(wndname, image);

    waitKey(0);

    for (i=0; i<RAND_N; i++) {

    Point org;

    org.x = rng.uniform(x1, x2);

    org.y = rng.uniform(y1, y2);

    putText(image, "OpenCV",org, rng.uniform(0,8),rng.uniform(0,10)*0.5+0.1,

            random_color(rng), rng.uniform(1, 10), line_type);

    }

    imshow(wndname, image);

    waitKey(0);

    return 0;

}

  1. RNG是OpenCV中的随机数生成类，其定义在core.hpp中，

    class CV_EXPORTS RNG
    
{
    
public:
    
    enum { UNIFORM=0, NORMAL=1 };

    RNG();
    
    RNG(uint64 _state);
    
    //! updates the state and returns the next 32-bit unsigned integer random number
    
    unsigned next();

    operator uchar();
    
    operator schar();
    
    operator ushort();
    
    operator short();
    
    operator unsigned();
    
    //! returns a random integer sampled uniformly from [0, N).
    
    unsigned operator()(unsigned N);
    
    unsigned operator ()();
    
    operator int();
    
    operator float();
    
    operator double();
    
    //! returns uniformly distributed integer random number from [a,b) range
    
    int uniform(int a, int b);
    
    //! returns uniformly distributed floating-point random number from [a,b) range
    
    float uniform(float a, float b);
    
    //! returns uniformly distributed double-precision floating-point random number from [a,b) range
    
    double uniform(double a, double b);
    
    void fill( InputOutputArray mat, int distType, InputArray a, InputArray b );
    
    //! returns Gaussian random variate with mean zero.
    
    double gaussian(double sigma);

    uint64 state;
    
};

    提供了两种随机数——均匀分布（uniform)和高斯正态分布（gaussian）。

    本文使用的是随机分布，两个參数分布表示均匀分布的下限和上限。

    RNG rng(0xFFFFFFFF);中的0xFFFFFFFF表示初始的随机值。

  2. Mat矩阵初始化：

    Mat image = Mat::zeros(height, width, CV_8UC3);

  3. line用于绘制直线，也定义在core.hpp中，

    //! draws the line segment (pt1, pt2) in the image
    
CV_EXPORTS_W void line(Mat& img, Point pt1, Point pt2, const Scalar&    color,int thickness=1, int lineType=8, int shift=0);

    还有其他画图函数circle、ellipse、rectangle等也也能够从core.hpp中找到原型。可用到时自行学习。

  4. putText能够将文字加入到图片中。

    //! renders text string in the image
    
CV_EXPORTS_W void putText( Mat& img, const string& text, Point org,
    
                         int fontFace, double fontScale, Scalar color,
    
                         int thickness=1, int linetype=8,
    
                         bool bottomLeftOrigin=false );

    其第一个參数img就是要加入文字的图像，第二个參数就是要加入的文字（程序中是"OpenCV"）

  5. 关于颜色：颜色是用RGB三通道表示的，因此上面函数中颜色參数的类型都是Scalar类型。Scalar在OpenCV中相似于向量，但其长度最大为4通道。源程序中

    Scalar(icolor&0xFF, (icolor>>8)&0xFF, (icolor>>16)&0xFF);

    将随机数的值取出分别作为RGB三个通道的颜色值。

效果

OpenCV基础篇之画图及RNG随机数对象

随机线条的效果

OpenCV基础篇之画图及RNG随机数对象

加入“OpenCV”文字后效果

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