opencv学习八

继续搬砖，opencv的core模块下的第六部分基本绘图：
我们打算画两个例子（原子和赌棍）， 所以必须创建两个图像和对应的窗口以显示。
/// 窗口名字
char atom_window[] = "Drawing 1: Atom";
char rook_window[] = "Drawing 2: Rook";
/// 创建空全黑像素的空图像
Mat atom_image = Mat::zeros( w, w, CV_8UC3 );
Mat rook_image = Mat::zeros( w, w, CV_8UC3 );
创建用来画不同几何形状的函数。比如用 MyEllipse 和 MyFilledCircle 来画原子。
/// 1. 画一个简单的原子。
/// 1.a. 创建椭圆
MyEllipse( atom_image, 90 );
MyEllipse( atom_image, 0 );
MyEllipse( atom_image, 45 );
MyEllipse( atom_image, -45 );
/// 1.b. 创建圆
MyFilledCircle( atom_image, Point( w/2.0, w/2.0) );
接下来用 MyLine*，*rectangle 和 a MyPolygon 来画赌棍：
/// 2. 画一个赌棍
/// 2.a. 创建一个凸多边形
MyPolygon( rook_image );
/// 2.b. 创建矩形
rectangle( rook_image,
           Point( 0, 7*w/8.0 ),
           Point( w, w),
           Scalar( 0, 255, 255 ),
           -1,
           8 );
/// 2.c. 画几条直线
MyLine( rook_image, Point( 0, 15*w/16 ), Point( w, 15*w/16 ) );
MyLine( rook_image, Point( w/4, 7*w/8 ), Point( w/4, w ) );
MyLine( rook_image, Point( w/2, 7*w/8 ), Point( w/2, w ) );
MyLine( rook_image, Point( 3*w/4, 7*w/8 ), Point( 3*w/4, w ) );
现在来看看每个函数内部如何定义:
MyLine
void MyLine( Mat img, Point start, Point end )
{
  int thickness = 2;
  int lineType = 8;
  line( img,
        start,
        end,
        Scalar( 0, 0, 0 ),
        thickness,
        lineType );
}
正如我们所见, MyLine 调用函数 line 来实现以下操作:
画一条从点 start 到点 end 的直线段
此线段将被画到图像 img 上
线的颜色由 Scalar( 0, 0, 0) 来定义，在此其相应RGB值为 黑色
线的粗细由 thickness 设定(此处设为 2)
此线为8联通 (lineType = 8)
MyEllipse
void MyEllipse( Mat img, double angle )
{
  int thickness = 2;
  int lineType = 8;
  ellipse( img,
           Point( w/2.0, w/2.0 ),
           Size( w/4.0, w/16.0 ),
           angle,
           0,
           360,
           Scalar( 255, 0, 0 ),
           thickness,
           lineType );
}
根据以上代码，我们可看到函数 ellipse 按照以下规则绘制椭圆：
椭圆将被画到图像 img 上
椭圆中心为点 (w/2.0, w/2.0) 并且大小位于矩形 (w/4.0, w/16.0) 内
椭圆旋转角度为 angle
椭圆扩展的弧度从 0 度到 360 度
图形颜色为 Scalar( 255, 255, 0) ，既蓝色
绘椭圆的线粗为 thickness ，此处是2
MyFilledCircle
void MyFilledCircle( Mat img, Point center )
{
 int thickness = -1;
 int lineType = 8;
 circle( img,
         center,
         w/32.0,
         Scalar( 0, 0, 255 ),
         thickness,
         lineType );
}
类似于椭圆函数，我们可以看到 circle 函数的参数意义如下：
圆将被画到图像 ( img )上
圆心由点 center 定义
圆的半径为: w/32.0
圆的颜色为: Scalar(0, 0, 255) ，按BGR的格式为 红色
线粗定义为 thickness = -1, 因此次圆将被填充
MyPolygon
void MyPolygon( Mat img )
{
  int lineType = 8;
  /** 创建一些点 */
  Point rook_points[1][20];
  rook_points[0][0] = Point( w/4.0, 7*w/8.0 );
  rook_points[0][1] = Point( 3*w/4.0, 7*w/8.0 );
  rook_points[0][2] = Point( 3*w/4.0, 13*w/16.0 );
  rook_points[0][3] = Point( 11*w/16.0, 13*w/16.0 );
  rook_points[0][4] = Point( 19*w/32.0, 3*w/8.0 );
  rook_points[0][5] = Point( 3*w/4.0, 3*w/8.0 );
  rook_points[0][6] = Point( 3*w/4.0, w/8.0 );
  rook_points[0][7] = Point( 26*w/40.0, w/8.0 );
  rook_points[0][8] = Point( 26*w/40.0, w/4.0 );
  rook_points[0][9] = Point( 22*w/40.0, w/4.0 );
  rook_points[0][10] = Point( 22*w/40.0, w/8.0 );
  rook_points[0][11] = Point( 18*w/40.0, w/8.0 );
  rook_points[0][12] = Point( 18*w/40.0, w/4.0 );
  rook_points[0][13] = Point( 14*w/40.0, w/4.0 );
  rook_points[0][14] = Point( 14*w/40.0, w/8.0 );
  rook_points[0][15] = Point( w/4.0, w/8.0 );
  rook_points[0][16] = Point( w/4.0, 3*w/8.0 );
  rook_points[0][17] = Point( 13*w/32.0, 3*w/8.0 );
  rook_points[0][18] = Point( 5*w/16.0, 13*w/16.0 );
  rook_points[0][19] = Point( w/4.0, 13*w/16.0) ;
  const Point* ppt[1] = { rook_points[0] };
  int npt[] = { 20 };
  fillPoly( img,
            ppt,
            npt,
            1,
            Scalar( 255, 255, 255 ),
            lineType );
 }
 我们用函数 :fill_poly:`fillPoly <>` 来绘制填充的多边形。请注意：
多边形将被画到图像 img 上
多边形的顶点集为 ppt
要绘制的多边形顶点数目为 npt
要绘制的多边形数量仅为 1
多边形的颜色定义为 Scalar( 255, 255, 255), 既BGR值为 白色
rectangle
rectangle( rook_image,
           Point( 0, 7*w/8.0 ),
           Point( w, w),
           Scalar( 0, 255, 255 ),
           -1,
           8 );
最后是函数:rectangle:rectangle <> （我们并没有为这家伙创建特定函数）。请注意：
矩形将被画到图像 rook_image 上
矩形两个对角顶点为 Point( 0, 7*w/8.0 ) 和 Point( w, w)
矩形的颜色为 Scalar(0, 255, 255) ，既BGR格式下的 黄色
由于线粗为 -1, 此矩形将被填充。

看一下完整的实现代码：

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

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>

#define w 400

using namespace cv;

/// Function headers
void MyEllipse(Mat img, double angle);
void MyFilledCircle(Mat img, Point center);
void MyPolygon(Mat img);
void MyLine(Mat img, Point start, Point end);

/**
* @function main
* @brief Main function
*/
int main(int argc, char **argv){

	/// Windows names
	char atom_window[] = "Drawing 1: Atom";
	char rook_window[] = "Drawing 2: Rook";

	/// Create black empty images 
	Mat atom_image = Mat::zeros(w, w, CV_8UC3);
	Mat rook_image = Mat::zeros(w, w, CV_8UC3);

	/// 1. Draw a simple atom:
	/// -----------------------

	/// 1.a. Creating ellipses 
	MyEllipse(atom_image, 90);
	MyEllipse(atom_image, 0);
	MyEllipse(atom_image, 45);
	MyEllipse(atom_image, -45);

	/// 1.b. Creating circles
	MyFilledCircle(atom_image, Point(w / 2.0, w / 2.0));

	/// 2. Draw a rook
	/// ------------------

	/// 2.a. Create a convex polygon
	MyPolygon(rook_image);

	/// 2.b. Creating rectangles
	rectangle(rook_image,
		Point(0, 7 * w / 8.0),
		Point(w, w),
		Scalar(0, 255, 255),
		-1,
		8);

	/// 2.c. Create a few lines 
	MyLine(rook_image, Point(0, 15 * w / 16), Point(w, 15 * w / 16));
	MyLine(rook_image, Point(w / 4, 7 * w / 8), Point(w / 4, w));
	MyLine(rook_image, Point(w / 2, 7 * w / 8), Point(w / 2, w));
	MyLine(rook_image, Point(3 * w / 4, 7 * w / 8), Point(3 * w / 4, w));

	/// 3. Display your stuff!
	imshow(atom_window, atom_image);
	cvMoveWindow(atom_window, 0, 200);
	imshow(rook_window, rook_image);
	cvMoveWindow(rook_window, w, 200);

	waitKey(0);
	return(0);
}

/// Function Declaration

/**
* @function MyEllipse
* @brief Draw a fixed-size ellipse with different angles
*/
void MyEllipse(Mat img, double angle)
{
	int thickness = 2;
	int lineType = 8;

	ellipse(img,
		Point(w / 2.0, w / 2.0),
		Size(w / 4.0, w / 16.0),
		angle,
		0,
		360,
		Scalar(255, 0, 0),
		thickness,
		lineType);
}

/**
* @function MyFilledCircle
* @brief Draw a fixed-size filled circle
*/
void MyFilledCircle(Mat img, Point center)
{
	int thickness = -1;
	int lineType = 8;

	circle(img,
		center,
		w / 32.0,
		Scalar(0, 0, 255),
		thickness,
		lineType);
}

/**
* @function MyPolygon
* @function Draw a simple concave polygon (rook)
*/
void MyPolygon(Mat img)
{
	int lineType = 8;

	/** Create some points */
	Point rook_points[1][20];
	rook_points[0][0] = Point(w / 4.0, 7 * w / 8.0);
	rook_points[0][1] = Point(3 * w / 4.0, 7 * w / 8.0);
	rook_points[0][2] = Point(3 * w / 4.0, 13 * w / 16.0);
	rook_points[0][3] = Point(11 * w / 16.0, 13 * w / 16.0);
	rook_points[0][4] = Point(19 * w / 32.0, 3 * w / 8.0);
	rook_points[0][5] = Point(3 * w / 4.0, 3 * w / 8.0);
	rook_points[0][6] = Point(3 * w / 4.0, w / 8.0);
	rook_points[0][7] = Point(26 * w / 40.0, w / 8.0);
	rook_points[0][8] = Point(26 * w / 40.0, w / 4.0);
	rook_points[0][9] = Point(22 * w / 40.0, w / 4.0);
	rook_points[0][10] = Point(22 * w / 40.0, w / 8.0);
	rook_points[0][11] = Point(18 * w / 40.0, w / 8.0);
	rook_points[0][12] = Point(18 * w / 40.0, w / 4.0);
	rook_points[0][13] = Point(14 * w / 40.0, w / 4.0);
	rook_points[0][14] = Point(14 * w / 40.0, w / 8.0);
	rook_points[0][15] = Point(w / 4.0, w / 8.0);
	rook_points[0][16] = Point(w / 4.0, 3 * w / 8.0);
	rook_points[0][17] = Point(13 * w / 32.0, 3 * w / 8.0);
	rook_points[0][18] = Point(5 * w / 16.0, 13 * w / 16.0);
	rook_points[0][19] = Point(w / 4.0, 13 * w / 16.0);

	const Point* ppt[1] = { rook_points[0] };
	int npt[] = { 20 };

	fillPoly(img,
		ppt,
		npt,
		1,
		Scalar(255, 255, 255),
		lineType);
}

/**
* @function MyLine
* @brief Draw a simple line
*/
void MyLine(Mat img, Point start, Point end)
{
	int thickness = 2;
	int lineType = 8;
	line(img,
		start,
		end,
		Scalar(0, 0, 0),
		thickness,
		lineType);
}

结果：