opencv学习（六）绘制图像与文字

使用cv::Point与cv::Scalar

Point表示2D平面上一个点x,y
             Point p; p.x = 10; p.y = 8;
             等价于  Point  p = Pont(10,8);

Scalar表示四个元素的向量
 Scalar(a, b, c);// a = blue, b = green, c = red表示RGB三个通道

绘制线、矩形、园、椭圆等基本几何形状

画线    cv::line 
画椭圆  cv::ellipse
画矩形  cv::rectangle
画圆    cv::circle
画填充  cv::fillPoly

1.绘制直线

 line( img, p1,p2, color, thickness, lineType，shift)
 img 原图
 p1，p2 起点、终点
 color 颜色
 thickness 粗细 一般为1
 lineType （LINE_4\LINE_8\LINE_AA） 
            8 (或忽略) - 8连接线.
            4 - 4连接线.
            CV_AA - 抗锯齿线.
shift  坐标中的小数位数.

实例：

void MyLines() {
	Point p1 = Point(20, 30);
	Point p2;
	p2.x = 400;
	p2.y = 400;
	Scalar color = Scalar(0, 0, 255);
	line(bgImage, p1, p2, color, 1, LINE_AA);
}

2.绘制椭圆

ellipse(img, center,axes,angle,startAngle, endAngle, color, thickness, lineType, shift)
center 椭圆中心
axes   椭圆主轴的一半
angle  椭圆旋转角度
startAngle 椭圆弧的起始角
endAngle   椭圆弧的结束角
color   线条颜色
thickness 粗细 一般为1
lineType  同上
shift     同上

实例：

void MyEllipse() {
	Scalar color = Scalar(0, 255, 0);
	ellipse(bgImage, Point(bgImage.cols / 2, bgImage.rows / 2), Size(bgImage.cols / 4, bgImage.rows / 8), 90, 0, 360, color, 2, LINE_8);
}

3.绘制矩形

rectangle( img, pt1, pt2,color,thickness=1,lineType, shift)

实例：

void MyRectangle() {
	Rect rect = Rect(200, 100, 300, 300);
	Scalar color = Scalar(255, 0, 0);
	rectangle(bgImage, rect, color, 2, LINE_8);
}

4.绘制圆

circle(img,  center, radius, color, thickness, lineType, shift)

实例：

void MyCircle() {
	Scalar color = Scalar(0, 255, 255);
	Point center = Point(bgImage.cols / 2, bgImage.rows / 2);
	circle(bgImage, center, 150, color, 2, 8);
}

5.画填充

fillPoly(img, pts, npts, ncontours, color, lineType, shift, Point offset=Point() )

实例：

void MyPolygon() {
	Point pts[1][5];
	pts[0][0] = Point(100, 100);
	pts[0][1] = Point(100, 200);
	pts[0][2] = Point(200, 200);
	pts[0][3] = Point(200, 100);
	pts[0][4] = Point(100, 100);

	const Point* ppts[] = { pts[0] };
	int npt[] = { 5 };
	Scalar color = Scalar(255, 12, 255);

	fillPoly(bgImage, ppts, npt, 1, color, 8);
}

6.绘制随机线条

putText(img,text,org, fontFace,fontScale,color,thickness,lineType，bottomLeftOrigin=false )
   

实例：

void RandomLineDemo() {
	RNG rng(12345);
	Point pt1;
	Point pt2;
	Mat bg = Mat::zeros(bgImage.size(), bgImage.type());
	namedWindow("random line demo", CV_WINDOW_AUTOSIZE);
	for (int i = 0; i < 100000; i++) {
		pt1.x = rng.uniform(0, bgImage.cols);
		pt2.x = rng.uniform(0, bgImage.cols);
		pt1.y = rng.uniform(0, bgImage.rows);
		pt2.y = rng.uniform(0, bgImage.rows);
		Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));
		if (waitKey(50) > 0) {
			break;
		}
		line(bg, pt1, pt2, color, 1, 8);
		imshow("random line demo", bg);
	}
}