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;
}

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。

Mat矩阵初始化：

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

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。

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"）

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