本次範例是在上一次部落格學習OpenCV範例（六）——基本繪圖的基礎上，加上随機數發生器和文字顯示，進行更加有趣的開發，當本次範例學習完之後，基本的繪圖函數也就學習完了。

1、介紹

範例通過使用随機數發生器類 (RNG) 并得到均勻分布的随機數，代入到繪制函數的參數裡面，使得産生各種各樣的圖案，通過使用函數 putText 顯示文字，最後通過循環，産生動态效果。

2、代碼實作

#include "stdafx.h"

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

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

using namespace cv;

/// Global Variables
const int NUMBER = 100;
const int DELAY = 5;

const int window_width = 900;
const int window_height = 600;
int x_1 = -window_width/2;
int x_2 = window_width*3/2;
int y_1 = -window_height/2;
int y_2 = window_height*3/2;

/// Function headers
static Scalar randomColor( RNG& rng );
int Drawing_Random_Lines( Mat image, char* window_name, RNG rng );//畫線
int Drawing_Random_Rectangles( Mat image, char* window_name, RNG rng );//畫矩形
int Drawing_Random_Ellipses( Mat image, char* window_name, RNG rng );//畫一些弧線
int Drawing_Random_Polylines( Mat image, char* window_name, RNG rng );// 畫一些折線
int Drawing_Random_Filled_Polygons( Mat image, char* window_name, RNG rng );// 畫被填充的多邊形
int Drawing_Random_Circles( Mat image, char* window_name, RNG rng );// 畫圓
int Displaying_Random_Text( Mat image, char* window_name, RNG rng );// 在随機的地方繪制文字
int Displaying_Big_End( Mat image, char* window_name, RNG rng );//顯示最後結果


/**
 * @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 );

  /// Initialize a matrix filled with zeros
  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 )
{
  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;
}

/**
 * @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;
}

3、運作結果

學習OpenCV（七）——随機數發生器和繪制文字1、介紹2、代碼實作3、運作結果4、用到的類和函數

點選這裡還可以看我錄制的關于程式運作的視訊，用手機拍的，效果不是很好，希望大神們可以給點建議，如何錄制視訊。

密碼為cool

4、用到的類和函數

RNG:

功能：随機數發生器

執行個體化一個發生器

用數值 0xFFFFFFFF 來執行個體化的一個RNG對象

RNG操作

功能：産生服從均勻分布的随機數

int RNG::uniform(int a, int b）
double RNG::gaussian(double sigma)
float RNG::uniform(float a, float b)double RNG::uniform(double a, double b)

a:随機數産生的左邊界，左邊界為閉區間

b:随機數産生的右邊界，右邊界為開區間

功能：産生服從高斯分布的随機數

double RNG::gaussian(double sigma)

sigma：高斯分布的标準差

polylines：

功能：畫多邊形曲線

結構：

void polylines(Mat& img, const Point** pts, const int* npts, int ncontours, bool isClosed, const Scalar& color, int thickness=1, int lineType=8, int shift=0 )

img：輸入圖檔

pts：多邊形頂點集

npts：要繪制的多邊形頂點數目

ncontours：要繪制的多邊形數目

isClosed：繪制的曲線是否閉合

color：顔色值

thickness：線的粗細程度，如果為負數，則說明圓内被填充。

lineType：線的類型，預設為8聯通

getTextSize：

功能：計算一個文本字元串的寬度和高度

結構：

getTextSize(const string& text, int fontFace, double fontScale, int thickness, int* baseLine)

text：文本字元串

fontFace：字型的類型

fontScale：字型的縮放比例

thickness：字型的粗細

baseLine:不知

putText:

功能：繪制文字

結構：

void putText(Mat& img, const string& text, Point org, int fontFace, double fontScale, Scalar color, int thickness=1, int lineType=8, bool bottomLeftOrigin=false )

img：輸入圖檔

text：繪制的文本

org：文字的左下角将用點 org 指定

fontFace：字型的類型

fontScale：字型的縮放比例

color：字型的顔色

thickness：字型的粗細

學習OpenCV（七）——随機數發生器和繪制文字1、介紹2、代碼實作3、運作結果4、用到的類和函數

1、介紹

2、代碼實作

3、運作結果

4、用到的類和函數

RNG:

polylines：

getTextSize：

putText:

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