OpenCV 2 计算机视觉编程手册读书笔记1
矩阵创建
Mat类是OpenCV中非常有用类，用来创建和操作多维矩阵。可以有很多方法构造它。
1 // 构造函数 2 //! constructs 2D matrix of the specified size and type 3 // (_type is CV_8UC1, CV_64FC3, CV_32SC(12) etc.) 4 Mat(int rows, int cols, int type); 5 Mat(Size size, int type); 6 //! constucts 2D matrix and fills it with the specified value _s. 7 Mat(int rows, int cols, int type, const Scalar& s); 8 Mat(Size size, int type, const Scalar& s); 9 10 // 感兴趣区域，部分区域，子区块，新的矩阵和m共同使用内存 11 //! creates a matrix header for a part of the bigger matrix 12 Mat(const Mat& m, const Range& rowRange, const Range& colRange=Range::all()); 13 Mat(const Mat& m, const Rect& roi); 14 Mat(const Mat& m, const Range* ranges); 15 16 // create()函数 17 Mat mat(2, 2, CV_8UC3); //构造函数创建矩阵 18 M.create(3, 2, CV_8UC2); //释放内存重新创建 19 20 // Matlab风格的创建方法 21 Mat zero = Mat::zeros(2, 3, CV_8UC1); 22 Mat one = Mat::ones(2, 3, CV32F); 23 Mat eye = Mat::eye(2, 3, CV_64F);
其中 type参数的值CV_8UC3，表示的是CV_8U类型，3通道，CV_8U即无符号8为数据。3通道相当于BGR通道。
图像读取
cv::imread( const string& filename, int flags);
读取指定的图片，flags可以有以下的值：
enum { /* 8bit, color or not */ CV_LOAD_IMAGE_UNCHANGED =-1, /* 8bit, gray */ CV_LOAD_IMAGE_GRAYSCALE =0, /* ?, color */ CV_LOAD_IMAGE_COLOR =1, /* any depth, ? */ CV_LOAD_IMAGE_ANYDEPTH =2, /* ?, any color */ CV_LOAD_IMAGE_ANYCOLOR =4 };
图像显示
1 // 先命名一个窗口，再使用 2 namedWindow( "output", CV_WINDOW_AUTOSIZE ); 3 imshow("input", img);
窗口可以有以下Type：
1 enum 2 { 3 //These 3 flags are used by cvSet/GetWindowProperty 4 CV_WND_PROP_FULLSCREEN = 0, //to change/get window's fullscreen property 5 CV_WND_PROP_AUTOSIZE = 1, //to change/get window's autosize property 6 CV_WND_PROP_ASPECTRATIO= 2, //to change/get window's aspectratio property 7 CV_WND_PROP_OPENGL = 3, //to change/get window's opengl support 8 9 //These 2 flags are used by cvNamedWindow and cvSet/GetWindowProperty 10 CV_WINDOW_NORMAL = 0x00000000, //the user can resize the window (no constraint) / also use to switch a fullscreen window to a normal size 11 CV_WINDOW_AUTOSIZE = 0x00000001, //the user cannot resize the window, the size is constrainted by the image displayed 12 CV_WINDOW_OPENGL = 0x00001000, //window with opengl support 13 14 //Those flags are only for Qt 15 CV_GUI_EXPANDED = 0x00000000, //status bar and tool bar 16 CV_GUI_NORMAL = 0x00000010, //old fashious way 17 18 //These 3 flags are used by cvNamedWindow and cvSet/GetWindowProperty 19 CV_WINDOW_FULLSCREEN = 1,//change the window to fullscreen 20 CV_WINDOW_FREERATIO = 0x00000100,//the image expends as much as it can (no ratio constraint) 21 CV_WINDOW_KEEPRATIO = 0x00000000//the ration image is respected. 22 };
图像存储
1 cv::imrwite("output.jpg", imgOut);
图像像素操作
at函数
1 void salt(cv::Mat &image, int n) 2 { 3 for(int k =0; k<n; ++k) 4 { 5 int i=rand()%image.cols; 6 int j=rand()%image.rows; 7 if(image.channels() == 1) // gray image 8 { 9 image.at<uchar>(j, i) = 255; 10 } 11 else if(image.channels() == 3) // color image 12 { 13 image.at<cv::Vec3b>(j, i)[0] = 255; 14 image.at<cv::Vec3b>(j, i)[1] = 255; 15 image.at<cv::Vec3b>(j, i)[2] = 255; 16 } 17 } 18 }
其中Vec3b的定义为：typedef Vec<uchar, 3> Vec3b。上述代码是在一个图片上随机产生盐点。
迭代器
1 cv::Mat Iterator_<cv::Vec3b> it; 2 // 定义在Mat_内部的迭代器 3 cv::Mat_<cv::Vec3b>::iterator it; 4 5 // 迭代器使用 6 void colorReduce(cv::Mat &image, int div=64) 7 { 8 // 得到初始位置的迭代器 9 cv::Mat_<cv::Vec3b>::iterator it = image.begin<cv::Vec3b>(); 10 // 得到种植位置的迭代器 11 cv::Mat_<cv::Vec3b>::iterator itend = image.edn<cv::Vec3b>(); 12 // 遍历所有像素 13 for(; it!=itend; ++it) 14 { 15 // 处理每个像素 16 (*it)[0] = (*it)[0]/div*div+div/2; 17 (*it)[1] = (*it)[0]/div*div+div/2; 18 (*it)[2] = (*it)[0]/div*div+div/2; 19 } 20 }
指针操作
// 得到image图像的第index行的首地址 image.ptr<uchar>(index);
图像算术运算
图像的算术运算可以有加减乘除，可以对图片有亮度有影响，具体的后续再了解。
图像感兴趣区域
图像感兴趣区域指的是，对一个图片的部分区域感兴趣，则可以只操作感兴趣的部分区域，也即子区域。