OpenCV学习：随机数发生器&绘制文字

opencv_tutorials学习

随机数发生器&绘制文字

学习知识点：

随机数发生器
直线、折现、矩形、圆、圆弧等的绘制
文字的显示
代码分析：

实例化Random Number Generator（随机数发生器对象）(RNG)
RNG的实现了一个随机数发生器。 在上面的例子中, rng 是用数值 0xFFFFFFFF 来实例化的一个RNG对象。

<span style="font-size:14px;color:#333333;">RNG rng( 0xFFFFFFFF ); </span>

主函数中的绘制图像程序调用

<span style="font-size:14px;color:#333333;">/// 现在我们先画线
c = Drawing_Random_Lines(image, window_name, rng);
if( c != 0 ) return 0;

/// 继续，这次是一些矩形
c = Drawing_Random_Rectangles(image, window_name, rng);
if( c != 0 ) return 0;

/// 画一些弧线
c = Drawing_Random_Ellipses( image, window_name, rng );
if( c != 0 ) return 0;

/// 画一些折线
c = Drawing_Random_Polylines( image, window_name, rng );
if( c != 0 ) return 0;

/// 画被填充的多边形
c = Drawing_Random_Filled_Polygons( image, window_name, rng );
if( c != 0 ) return 0;

/// 画圆
c = Drawing_Random_Circles( image, window_name, rng );
if( c != 0 ) return 0;

/// 在随机的地方绘制文字
c = Displaying_Random_Text( image, window_name, rng );
if( c != 0 ) return 0;

/// Displaying the big end!
c = Displaying_Big_End( image, window_name, rng );</span>

函数Drawing_Random_Lines

<span style="font-size:14px;color:#333333;">int Drawing_Random_Lines( Mat image, char* window_name, RNG rng )
{
int lineType = 8;
Point pt1, pt2;

for( int i = 0; i < NUMBER; i++ )
{
pt1.x = rng.uniform( x_1, x_2 );
pt1.y = rng.uniform( y_1, y_2 );
pt2.x = rng.uniform( x_1, x_2 );
pt2.y = rng.uniform( y_1, y_2 );

line( image, pt1, pt2, randomColor(rng), rng.uniform(1, 10), 8 );
imshow( window_name, image );
if( waitKey( DELAY ) >= 0 )
{ return -1; }
}
return 0;
}</span>

其中，for循环NUMBER次

随机颜色产生函数

<span style="font-size:14px;color:#333333;">static Scalar randomColor( RNG& rng )
{
int icolor = (unsigned) rng;
return Scalar( icolor&255, (icolor>>8)&255, (icolor>>16)&255 );
}</span>

Display_Random_Text函数

<span style="font-size:14px;color:#333333;">int Displaying_Random_Text( Mat image, char* window_name, RNG rng )
{
int lineType = 8;

for ( int i = 1; i < NUMBER; i++ )
{
Point org;
org.x = rng.uniform(x_1, x_2);
org.y = rng.uniform(y_1, y_2);

putText( image, "Testing text rendering", org, rng.uniform(0,8),
rng.uniform(0,100)*0.05+0.1, randomColor(rng), rng.uniform(1, 10), lineType);

imshow( window_name, image );
if( waitKey(DELAY) >= 0 )
{ return -1; }
}

return 0;
}</span>

其中，putText函数说明如下：

在 image 上绘制文字 “Testing text rendering” 。
文字的左下角将用点 org 指定。
字体参数是用一个在 

 之间的整数来定义。
字体的缩放比例是用表达式 rng.uniform(0, 100)x0.05 + 0.1 指定(表示它的范围是 

)。
字体的颜色是随机的 (记为 randomColor(rng))。
字体的粗细范围是从 1 到 10, 表示为 rng.uniform(1,10)  

附录：opencv提供的函数实现（自己写的注释，请谨慎参考）

/**
* @file Drawing_2.cpp
* @brief Simple sample code
*/

#include <opencv2/core/core.hpp> //opencv头文件
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
#include <stdio.h>

using namespace cv; //使用命名空间

/// Global Variables
const int NUMBER = 100; //定义整形常量
const int DELAY = 5;

const int window_width = 900; //窗口大小定义
const int window_height = 600;
int x_1 = -window_width/2;
int x_2 = window_width*3/2;
int y_1 = -window_width/2;
int y_2 = window_width*3/2;

/// Function headers 函数说明
static Scalar randomColor( RNG& rng );
int Drawing_Random_Lines( Mat image, char* window_name, RNG rng );
int Drawing_Random_Rectangles( Mat image, char* window_name, RNG rng );
int Drawing_Random_Ellipses( Mat image, char* window_name, RNG rng );
int Drawing_Random_Polylines( Mat image, char* window_name, RNG rng );
int Drawing_Random_Filled_Polygons( Mat image, char* window_name, RNG rng );
int Drawing_Random_Circles( Mat image, char* window_name, RNG rng );
int Displaying_Random_Text( Mat image, char* window_name, RNG rng );
int Displaying_Big_End( Mat image, char* window_name, RNG rng );

/**
* @function main
*/
int main( void )
{
int c;

/// Start creating a window
char window_name[] = "Drawing_2 Tutorial";

/// Also create a random object (RNG)
RNG rng( 0xFFFFFFFF ); //实例化一个 Random Number Generator（随机数发生器对象） (RNG) Q_yyt:这个没看懂！

/// Initialize a matrix filled with zeros 初始化一个数组，填充为0
Mat image = Mat::zeros( window_height, window_width, CV_8UC3 );
/// Show it in a window during DELAY ms
imshow( window_name, image );
waitKey( DELAY );

/// Now, let's draw some lines
c = Drawing_Random_Lines(image, window_name, rng);
if( c != 0 ) return 0;

/// Go on drawing, this time nice rectangles
c = Drawing_Random_Rectangles(image, window_name, rng);
if( c != 0 ) return 0;

/// Draw some ellipses
c = Drawing_Random_Ellipses( image, window_name, rng );
if( c != 0 ) return 0;

/// Now some polylines
c = Drawing_Random_Polylines( image, window_name, rng );
if( c != 0 ) return 0;

/// Draw filled polygons
c = Drawing_Random_Filled_Polygons( image, window_name, rng );
if( c != 0 ) return 0;

/// Draw circles
c = Drawing_Random_Circles( image, window_name, rng );
if( c != 0 ) return 0;

/// Display text in random positions
c = Displaying_Random_Text( image, window_name, rng );
if( c != 0 ) return 0;

/// Displaying the big end!
c = Displaying_Big_End( image, window_name, rng );
if( c != 0 ) return 0;

waitKey(0);
return 0;
}

/// Function definitions

/**
* @function randomColor
* @brief Produces a random color given a random object
*/
static Scalar randomColor( RNG& rng )
{
int icolor = (unsigned) rng;
return Scalar( icolor&255, (icolor>>8)&255, (icolor>>16)&255 );
}

/**
* @function Drawing_Random_Lines
*/
int Drawing_Random_Lines( Mat image, char* window_name, RNG rng )//画随机线条 NUMBER条
{
Point pt1, pt2;

for( int i = 0; i < NUMBER; i++ )
{
pt1.x = rng.uniform( x_1, x_2 ); //产生在x_1 x_2之间均匀分布的随机数
pt1.y = rng.uniform( y_1, y_2 );
pt2.x = rng.uniform( x_1, x_2 );
pt2.y = rng.uniform( y_1, y_2 );

line( image, pt1, pt2, randomColor(rng), rng.uniform(1, 10), 8 );
imshow( window_name, image );
if( waitKey( DELAY ) >= 0 )
{ return -1; }
}

return 0;
}

/**
* @function Drawing_Rectangles
*/
int Drawing_Random_Rectangles( Mat image, char* window_name, RNG rng )
{
Point pt1, pt2;
int lineType = 8;
int thickness = rng.uniform( -3, 10 );

for( int i = 0; i < NUMBER; i++ )
{
pt1.x = rng.uniform( x_1, x_2 );
pt1.y = rng.uniform( y_1, y_2 );
pt2.x = rng.uniform( x_1, x_2 );
pt2.y = rng.uniform( y_1, y_2 );

rectangle( image, pt1, pt2, randomColor(rng), MAX( thickness, -1 ), lineType );

imshow( window_name, image );
if( waitKey( DELAY ) >= 0 )
{ return -1; }
}

return 0;
}

/**
* @function Drawing_Random_Ellipses
*/
int Drawing_Random_Ellipses( Mat image, char* window_name, RNG rng )
{
int lineType = 8;

for ( int i = 0; i < NUMBER; i++ )
{
Point center;
center.x = rng.uniform(x_1, x_2);
center.y = rng.uniform(y_1, y_2);

Size axes;
axes.width = rng.uniform(0, 200);
axes.height = rng.uniform(0, 200);

double angle = rng.uniform(0, 180);

ellipse( image, center, axes, angle, angle - 100, angle + 200,
randomColor(rng), rng.uniform(-1,9), lineType );

imshow( window_name, image );

if( waitKey(DELAY) >= 0 )
{ return -1; }
}

return 0;
}

/**
* @function Drawing_Random_Polylines
*/
int Drawing_Random_Polylines( Mat image, char* window_name, RNG rng )
{
int lineType = 8;

for( int i = 0; i< NUMBER; i++ )
{
Point pt[2][3];
pt[0][0].x = rng.uniform(x_1, x_2);
pt[0][0].y = rng.uniform(y_1, y_2);
pt[0][1].x = rng.uniform(x_1, x_2);
pt[0][1].y = rng.uniform(y_1, y_2);
pt[0][2].x = rng.uniform(x_1, x_2);
pt[0][2].y = rng.uniform(y_1, y_2);
pt[1][0].x = rng.uniform(x_1, x_2);
pt[1][0].y = rng.uniform(y_1, y_2);
pt[1][1].x = rng.uniform(x_1, x_2);
pt[1][1].y = rng.uniform(y_1, y_2);
pt[1][2].x = rng.uniform(x_1, x_2);
pt[1][2].y = rng.uniform(y_1, y_2);

const Point* ppt[2] = {pt[0], pt[1]};
int npt[] = {3, 3};

polylines(image, ppt, npt, 2, true, randomColor(rng), rng.uniform(1,10), lineType);

imshow( window_name, image );
if( waitKey(DELAY) >= 0 )
{ return -1; }
}
return 0;
}

/**
* @function Drawing_Random_Filled_Polygons
*/
int Drawing_Random_Filled_Polygons( Mat image, char* window_name, RNG rng )
{
int lineType = 8;

for ( int i = 0; i < NUMBER; i++ )
{
Point pt[2][3];
pt[0][0].x = rng.uniform(x_1, x_2);
pt[0][0].y = rng.uniform(y_1, y_2);
pt[0][1].x = rng.uniform(x_1, x_2);
pt[0][1].y = rng.uniform(y_1, y_2);
pt[0][2].x = rng.uniform(x_1, x_2);
pt[0][2].y = rng.uniform(y_1, y_2);
pt[1][0].x = rng.uniform(x_1, x_2);
pt[1][0].y = rng.uniform(y_1, y_2);
pt[1][1].x = rng.uniform(x_1, x_2);
pt[1][1].y = rng.uniform(y_1, y_2);
pt[1][2].x = rng.uniform(x_1, x_2);
pt[1][2].y = rng.uniform(y_1, y_2);

const Point* ppt[2] = {pt[0], pt[1]};
int npt[] = {3, 3};

fillPoly( image, ppt, npt, 2, randomColor(rng), lineType );

imshow( window_name, image );
if( waitKey(DELAY) >= 0 )
{ return -1; }
}
return 0;
}

/**
* @function Drawing_Random_Circles
*/
int Drawing_Random_Circles( Mat image, char* window_name, RNG rng )
{
int lineType = 8;

for (int i = 0; i < NUMBER; i++)
{
Point center;
center.x = rng.uniform(x_1, x_2);
center.y = rng.uniform(y_1, y_2);

circle( image, center, rng.uniform(0, 300), randomColor(rng),
rng.uniform(-1, 9), lineType );

imshow( window_name, image );
if( waitKey(DELAY) >= 0 )
{ return -1; }
}

return 0;
}

/**
* @function Displaying_Random_Text
*/
int Displaying_Random_Text( Mat image, char* window_name, RNG rng )
{
int lineType = 8;

for ( int i = 1; i < NUMBER; i++ )
{
Point org;
org.x = rng.uniform(x_1, x_2);
org.y = rng.uniform(y_1, y_2);

putText( image, "Testing text rendering", org, rng.uniform(0,8),
rng.uniform(0,100)*0.05+0.1, randomColor(rng), rng.uniform(1, 10), lineType);

imshow( window_name, image );
if( waitKey(DELAY) >= 0 )
{ return -1; }
}

return 0;
}

/**
* @function Displaying_Big_End
*/
int Displaying_Big_End( Mat image, char* window_name, RNG )
{
Size textsize = getTextSize("OpenCV forever!", FONT_HERSHEY_COMPLEX, 3, 5, 0);
Point org((window_width - textsize.width)/2, (window_height - textsize.height)/2);
int lineType = 8;

Mat image2;

for( int i = 0; i < 255; i += 2 )
{
image2 = image - Scalar::all(i);
putText( image2, "OpenCV forever!", org, FONT_HERSHEY_COMPLEX, 3,
Scalar(i, i, 255), 5, lineType );

imshow( window_name, image2 );
if( waitKey(DELAY) >= 0 )
{ return -1; }
}

return 0;
}