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)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::vector >, 获取轮廓面积的时候输入的轮廓参数是 std::vector
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
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
https://blog.csdn.net/caomin1hao/article/details/81876836
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