OpenCV基础篇之画图及RNG随机数对象

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

随机线条的效果

加入“OpenCV”文字后效果