open_cv_computer_vision_part1

mat

 // create image
 cv:Mat function(){
     cv::Mat ima(500,500,CV_8U,50);
     return ima;
 }
 // create a new image made of 240 rows and 320 columns
 cv::Mat image1(240,320,CV_8U,100);
 // or:
 cv::Mat image1(240,320,CV_8U,cv::Scalar(100));
 // re-allocate a new image
 // (only if size or type are different)
 image1.create(200,200,CV_8U);
 image1= 200;
 cv::imshow("Image", image1); // show the image
 // create a red color image
 // channel order is BGR
 cv::Mat image2(240,320,CV_8UC3,cv::Scalar(0,0,255));
 // or:
 cv::Mat image2(cv::Size(320,240),CV_8UC3);
 image2= cv::Scalar(0,0,255);
 cv::imshow("Image", image2); // show the image
 // read an image
 cv::Mat image3=  cv::imread("puppy.bmp"); 
 // all these images point to the same data block
 cv::Mat image4(image3);
 image1= image3;
 // these images are new copies of the source image
 image3.copyTo(image2);
 cv::Mat image5= image3.clone();
 // transform the image for testing
 cv::flip(image3,image3,1); 
 // get a gray-level image from a function
 cv::Mat gray= function();
 // read the image in gray scale
 image1=  cv::imread("puppy.bmp", CV_LOAD_IMAGE_GRAYSCALE); 
 // convert the image into a floating point image [0,1]
 image1.convertTo(image2,CV_32F,1/255.0,0.0);
 cv::imshow("Image", image2); // show the image
 // Test cv::Matx
 // a 3x3 matrix of double-precision
 cv::Matx33d matrix(3.0, 2.0, 1.0,
                    2.0, 1.0, 3.0,
                    1.0, 2.0, 3.0);
 // a 3x1 matrix (a vector)
 cv::Matx31d vector(5.0, 1.0, 3.0);
 // multiplication
 cv::Matx31d result = matrix*vector;

logo

 // define an image window
 cv::namedWindow("Image"); 
 // read the image 
 cv::Mat image=  cv::imread("puppy.bmp"); 
 // read the logo
 cv::Mat logo=  cv::imread("smalllogo.png"); 
 // define image ROI at image bottom-right
 cv::Mat imageROI(image, 
               cv::Rect(image.cols-logo.cols, //ROI coordinates
                        image.rows-logo.rows,
                        logo.cols,logo.rows));// ROI size
 // insert logo
 logo.copyTo(imageROI);
 cv::imshow("Image", image); // show the image
 // re-read the original image
 image=  cv::imread("puppy.bmp");
 // define image ROI at image bottom-right
 imageROI= image(cv::Rect(image.cols-logo.cols,image.rows-logo.rows,
                          logo.cols,logo.rows));
 // or using ranges:
 imageROI= image(cv::Range(image.rows-logo.rows,image.rows), 
                 cv::Range(image.cols-logo.cols,image.cols));
 // use the logo as a mask (must be gray-level)
 cv::Mat mask(logo);
 // insert by copying only at locations of non-zero mask
 logo.copyTo(imageROI,mask);

load,display,save

 cv::Mat image;
 image.rows;
 image.cols;
 image = cv::imread('puppy.bmp',cv::IMREAD_GRAYSCALE);
 image.empty();//是否为空
 image.channels();
 cv::namedWindow('Original Image');
 cv::imshow('Original Image',image);
 cv::setMouseCallback('Original Image', onMouse, reinterpret_cast<void*>(&image));
 cv::Mat result:
 cv::flip(image,result,1);
 cv::namedWindow("Output Image");
 cv::imshow("Output Image", result);
 cv::imwrite("output.bmp",result);
 cv::circle(image,                   //destination image
            cv::Point(155,110),)     //center coordinate
            65,                      //radius
            0,                       //color
            3,)                      //thickness
 cv::putText(image,                  //destination image
            "this is a dog.",        //test
            cv::Point(40,200),       //text position 
            cv::FONT_HERSHEY_PLAIN,  //font type
            2.0,                     //font scale
            255,                     //text color
            2)                       //text thickness