opencv c 学习笔记

1. createTrackbar是Opencv中的API，其可在显示图像的窗口中快速创建一个滑动控件，用于手动调节阈值，具有非常直观的效果。具体定义如下：

    CV_EXPORTS int createTrackbar(const string& trackbarname, const string& winname,
                                  int* value, int count,
                                  TrackbarCallback onChange = 0,
                                  void* userdata = 0);

形式参数一、trackbarname：滑动空间的名称；

形式参数二、winname：滑动空间用于依附的图像窗口的名称；

形式参数三、value：初始化阈值；

形式参数四、count：滑动控件的刻度范围；

形式参数五、TrackbarCallback是回调函数，其定义如下：

typedef void (CV_CDECL *TrackbarCallback)(int pos, void* userdata);

参考： https://blog.csdn.net/mysee1989/article/details/41379817
https://docs.opencv.org/3.4.1/dc/dfa/Morphology_1_8cpp-example.html#a20

2. Rect 是矩形类，成员变量x、y、width、height，分别为左上角点的坐标和矩形的宽和高。常用的成员函数有Size()返回值为一个Size，area()返回矩形的面积，contains(Point)用来判断点是否在矩形内，inside(Rect)函数判断矩形是否在该矩形内，tl()返回左上角点坐标，br()返回右下角点坐标。

Rect类的使用

    rect = rect ± point (shifting a rectangle by a certain offset)
    rect = rect ± size (expanding or shrinking a rectangle by a certain amount)
    rect += point, rect -= point, rect += size, rect -= size (augmenting operations)
    rect = rect1 & rect2 (rectangle intersection)
    rect = rect1 | rect2 (minimum area rectangle containing rect1 and rect2 )
    rect &= rect1, rect |= rect1 (and the corresponding augmenting operations)
    rect == rect1, rect != rect1 (rectangle comparison)

参考： https://www.cnblogs.com/happyamyhope/p/9844629.html

3. copyTo 是深拷贝，但是要根据大小信息，决定是否重新申请空间，clone 不管大小信息，全部重新申请空间进行深拷贝。

参考： https://blog.csdn.net/u013806541/article/details/70154719

4. opencv 提供的字符串格式化如下：

string formated_str = format("I have made %d dollars on this product.", 500);

参考： https://blog.csdn.net/yiyeshuanglinzui/article/details/108388683

5. 获取矩阵的行，列，位数。

Mat(int rows, int cols, int type)， 直接使用属性就行。

m.rows
m.cols

参考： https://blog.csdn.net/renweiyi1487/article/details/101616758

6. 添加文字， putText

void cv::putText 	( 	InputOutputArray  	img,
		const String &  	text,
		Point  	org,
		int  	fontFace,
		double  	fontScale,
		Scalar  	color,
		int  	thickness = 1,
		int  	lineType = LINE_8,
		bool  	bottomLeftOrigin = false 
	) 	

	cv::putText(image, text, origin, font_face, font_scale, cv::Scalar(0, 255, 255), thickness, 8, 0);

参考：https://docs.opencv.org/3.4/d6/d6e/group__imgproc__draw.html#ga5126f47f883d730f633d74f07456c576
https://blog.csdn.net/guduruyu/article/details/68491211

7. imutils 有 c++ 的部分实现，https://github.com/minooei/imutils

8. 获得轮廓最小矩形，使用 boundingRect

Rect boundRect = boundingRect( contours_poly[i] );

参考： https://docs.opencv.org/3.4/da/d0c/tutorial_bounding_rects_circles.html

9. 矩形 rectangle()

void cv::rectangle 	( 	InputOutputArray  	img,
		Point  	pt1,
		Point  	pt2,
		const Scalar &  	color,
		int  	thickness = 1,
		int  	lineType = LINE_8,
		int  	shift = 0 
	) 	
void cv::rectangle 	( 	Mat &  	img,
		Rect  	rec,
		const Scalar &  	color,
		int  	thickness = 1,
		int  	lineType = LINE_8,
		int  	shift = 0 
	) 	

rectangle(src, boundRect[i], Scalar(0, 255, 0));
rectangle(flipFrame, Point(roi_ws, roi_hs), Point(roi_we, roi_he), Scalar(0, 255, 0), 0)

参考： https://docs.opencv.org/3.4/d6/d6e/group__imgproc__draw.html#ga07d2f74cadcf8e305e810ce8eed13bc9
https://kknews.cc/code/66yekj3.html

10. 获得轮廓最小面积

◆ contourArea()
double cv::contourArea 	( 	InputArray  	contour,
		bool  	oriented = false 
	) 	

fabs(contourArea(Mat(c)));

参考： https://docs.opencv.org/master/d3/dc0/group__imgproc__shape.html#ga2c759ed9f497d4a618048a2f56dc97f1
https://docs.opencv.org/3.4.1/dd/d9d/segment_objects_8cpp-example.html#a1

11. 膨胀

◆ dilate()
void cv::dilate 	( 	InputArray  	src,
		OutputArray  	dst,
		InputArray  	kernel,
		Point  	anchor = Point(-1,-1),
		int  	iterations = 1,
		int  	borderType = BORDER_CONSTANT,
		const Scalar &  	borderValue = morphologyDefaultBorderValue() 
	) 	

dilate(mid_filer,gray_dilate1,element);

参考： https://docs.opencv.org/3.4/d4/d86/group__imgproc__filter.html#ga4ff0f3318642c4f469d0e11f242f3b6c
https://www.itread01.com/articles/1478557515.html
https://docs.opencv.org/3.4.1/d8/dc0/morphology2_8cpp-example.html#a10
https://zhuanlan.zhihu.com/p/40326127
https://www.jianshu.com/p/ee72f5215e07
https://www.cnblogs.com/ssyfj/p/9276999.html

12. 查找轮廓

	findContours(image,contours,hierarchy,RETR_TREE,CHAIN_APPROX_SIMPLE,Point());

查找轮廓的参数导致的结果，参考： https://blog.csdn.net/dcrmg/article/details/51987348

13. mat 的创建，复制和释放，构造函数等等

参考： https://blog.csdn.net/wanggao_1990/article/details/53150926
https://blog.csdn.net/guyuealian/article/details/70159660

14. createTrackbar 用于创建滑动控件，方便调试效果。

参考： https://blog.csdn.net/u013270326/article/details/72821149

15. 求差 absdiff

absdiff(frameNow,framePre,frameDet);

参考： https://blog.csdn.net/dcrmg/article/details/52234929

16. 翻转图像

flip()
void cv::flip 	( 	InputArray  	src,
		OutputArray  	dst,
		int  	flipCode 
	) 	

参考： https://docs.opencv.org/3.4/d2/de8/group__core__array.html#gaca7be533e3dac7feb70fc60635adf441

17. 截取部分矩阵

◆ Mat() [15/29]
cv::Mat::Mat 	( 	const Mat &  	m,
		const Range &  	rowRange,
		const Range &  	colRange = Range::all() 
	) 	

roiFrame = Mat(flipFrame, Range(roi_hs, roi_he), Range(roi_ws, roi_we));

参考： https://docs.opencv.org/master/d3/d63/classcv_1_1Mat.html#a92a3e9e5911a2eb0cf0950a0a9670c76

18. 转换颜色

◆ cvtColor()
void cv::cvtColor 	( 	InputArray  	src,
		OutputArray  	dst,
		int  	code,
		int  	dstCn = 0 
	) 	

cvtColor(roiFrame, hsvFrame, COLOR_BGR2HSV)

参考： https://docs.opencv.org/3.4/d8/d01/group__imgproc__color__conversions.html#ga397ae87e1288a81d2363b61574eb8cab

19. 通过上下限阈值从图像中提取作为前景，其他作为后景，完成图像的二值化。

inRange()
void cv::inRange 	( 	InputArray  	src,
		InputArray  	lowerb,
		InputArray  	upperb,
		OutputArray  	dst 
	) 	

inRange(hsvFrame, Scalar(0, 20, 70), Scalar(20, 255, 255), maskFrame);

参考： https://docs.opencv.org/master/d2/de8/group__core__array.html#ga48af0ab51e36436c5d04340e036ce981
https://docs.opencv.org/master/d6/d7f/samples_2cpp_2camshiftdemo_8cpp-example.html#a33

20. 寻找轮廓 findContours 获得的轮廓类型是： std::vector<std::vectorcv::Point >, 获取轮廓面积的时候输入的轮廓参数是 std::vectorcv::Point

参考： https://docs.opencv.org/master/d3/dc0/group__imgproc__shape.html#gadf1ad6a0b82947fa1fe3c3d497f260e0
https://docs.opencv.org/master/d3/dc0/group__imgproc__shape.html#ga2c759ed9f497d4a618048a2f56dc97f1

21. 画轮廓线

◆ drawContours()
void cv::drawContours 	( 	InputOutputArray  	image,
		InputArrayOfArrays  	contours,
		int  	contourIdx,
		const Scalar &  	color,
		int  	thickness = 1,
		int  	lineType = LINE_8,
		InputArray  	hierarchy = noArray(),
		int  	maxLevel = INT_MAX,
		Point  	offset = Point() 
	) 	

参考： https://docs.opencv.org/master/d6/d6e/group__imgproc__draw.html#ga746c0625f1781f1ffc9056259103edbc

22. 计算曲线长度或者轮廓周长。

◆ arcLength()
double cv::arcLength 	( 	InputArray  	curve,
		bool  	closed 
	) 	

参考： https://docs.opencv.org/master/d3/dc0/group__imgproc__shape.html#ga8d26483c636be6b35c3ec6335798a47c

23. 计算轮廓近似多边形

◆ approxPolyDP()
void cv::approxPolyDP 	( 	InputArray  	curve,
		OutputArray  	approxCurve,
		double  	epsilon,
		bool  	closed 
	) 	

参考： https://docs.opencv.org/master/d3/dc0/group__imgproc__shape.html#ga0012a5fdaea70b8a9970165d98722b4c

24. 计算凸包

◆ convexHull()
void cv::convexHull 	( 	InputArray  	points,
		OutputArray  	hull,
		bool  	clockwise = false,
		bool  	returnPoints = true 
	) 	

参考： https://docs.opencv.org/master/d3/dc0/group__imgproc__shape.html#ga014b28e56cb8854c0de4a211cb2be656

25. 计算凸性缺陷

◆ convexityDefects()
void cv::convexityDefects 	( 	InputArray  	contour,
		InputArray  	convexhull,
		OutputArray  	convexityDefects 
	) 	

注意： contour 是 vector， convexhull 是 vector，convexityDefects 是 vector。

如果有报错： OpenCV Error: Assertion failed (hpoints > 0) in convexityDefects, file /home/neha/opencv-3.4.0/modules/imgproc/src/convhull.cpp, line 284 terminate called after throwing an instance of 'cv::Exception' what(): /home/neha/opencv-3.4.0/modules/imgproc/src/convhull.cpp:284: error:
(-215) hpoints > 0 in function convexityDefects
那么需要检查 convexhull 是不是 vector。

参考： https://docs.opencv.org/master/d3/dc0/group__imgproc__shape.html#gada4437098113fd8683c932e0567f47ba
https://github.com/wonderseen/Sparse-Points-Gen-Convex/issues/1

26. Vec4i 是 4个 int 组成的 vector 向量，即 vector

参考： https://www.coder.work/article/826469

27. 画圆圈。

◆ circle()
void cv::circle 	( 	InputOutputArray  	img,
		Point  	center,
		int  	radius,
		const Scalar &  	color,
		int  	thickness = 1,
		int  	lineType = LINE_8,
		int  	shift = 0 
	) 	

参考： https://docs.opencv.org/master/d6/d6e/group__imgproc__draw.html#gaf10604b069374903dbd0f0488cb43670

28. 画线

◆ line()
void cv::line 	( 	InputOutputArray  	img,
		Point  	pt1,
		Point  	pt2,
		const Scalar &  	color,
		int  	thickness = 1,
		int  	lineType = LINE_8,
		int  	shift = 0 
	) 	

参考： https://docs.opencv.org/master/d6/d6e/group__imgproc__draw.html#ga7078a9fae8c7e7d13d24dac2520ae4a2

29. 高斯模糊

◆ GaussianBlur()
void cv::GaussianBlur 	( 	InputArray  	src,
		OutputArray  	dst,
		Size  	ksize,
		double  	sigmaX,
		double  	sigmaY = 0,
		int  	borderType = BORDER_DEFAULT 
	)

模糊参数的影响效果可以参考： https://www.cnblogs.com/sdu20112013/p/11600436.html

参考： https://docs.opencv.org/master/d4/d86/group__imgproc__filter.html#gaabe8c836e97159a9193fb0b11ac52cf1

30. 手势识别，用到凸包和缺陷。

具体可参考： http://www.zfhblog.com/index.php/archives/22/
https://www.cnblogs.com/Anita9002/p/5332122.html
https://docs.opencv.org/master/d7/d1d/tutorial_hull.html
https://blog.csdn.net/lichengyu/article/details/38392473

31. resize

    cv::Mat dst(300, 300, image.type());
    cv::resize(image, dst, dst.size(), 0, 0, cv::INTER_LINEAR);

参考： https://blog.csdn.net/i_chaoren/article/details/54564663
https://blog.csdn.net/u012005313/article/details/51943442
https://www.jianshu.com/p/11879a49d1a0

32. 复制所有的图像数据

    cv::Mat image;
    image = cv::imread(imgPath);
    memcpy(data, image.data, image.dataend - image.datastart);

参考: https://www.jianshu.com/p/cfc0c1f87bf8

33. 清除图像数据

Mat mat3 = Mat::zeros(1, 4, CV_32F);
mat3.release();

参考: https://blog.csdn.net/wanggao_1990/article/details/53150926