7.OpenCv矩阵的掩码操作

程序来源：F:\opencv\opencv\samples\cpp\tutorial_code\core\mat_mask_operations

程序：

#include <opencv2/core/core.hpp>#include <opencv2/highgui/highgui.hpp>#include <opencv2/imgproc/imgproc.hpp>#include <iostream>using namespace std;using namespace cv;void help(char* progName){    cout << endl        <<  "This program shows how to filter images with mask: the write it yourself and the"        << "filter2d way. " << endl        <<  "Usage:"                                                                        << endl        << progName << " [image_name -- default lena.jpg] [G -- grayscale] "        << endl << endl;}void Sharpen(const Mat& myImage,Mat& Result);int main( int argc, char* argv[]){    help(argv[0]);    const char* filename = argc >=2 ? argv[1] : "lena.jpg";    Mat I, J, K;    if (argc >= 3 && !strcmp("G", argv[2]))        I = imread( filename, CV_LOAD_IMAGE_GRAYSCALE);    else        I = imread( filename, CV_LOAD_IMAGE_COLOR);    namedWindow("Input", CV_WINDOW_AUTOSIZE);    namedWindow("Output", CV_WINDOW_AUTOSIZE);    imshow("Input", I);    double t = (double)getTickCount();    Sharpen(I, J);    t = ((double)getTickCount() - t)/getTickFrequency();    cout << "Hand written function times passed in seconds: " << t << endl;    imshow("Output", J);    cvWaitKey(0);    Mat kern = (Mat_<char>(3,3) <<  0, -1,  0,                                   -1,  5, -1,                                    0, -1,  0);    t = (double)getTickCount();    filter2D(I, K, I.depth(), kern );    t = ((double)getTickCount() - t)/getTickFrequency();    cout << "Built-in filter2D time passed in seconds:      " << t << endl;    imshow("Output", K);    cvWaitKey(0);    return 0;}void Sharpen(const Mat& myImage,Mat& Result){    CV_Assert(myImage.depth() == CV_8U);  // accept only uchar images                                      //若该函数括号内的表达式为false，则会抛出一个错误    const int nChannels = myImage.channels();    Result.create(myImage.size(),myImage.type());    for(int j = 1 ; j < myImage.rows-1; ++j)    {        const uchar* previous = myImage.ptr<uchar>(j - 1);//前一行像素的指针const uchar* current  = myImage.ptr<uchar>(j    );//当前行像素的指针        const uchar* next     = myImage.ptr<uchar>(j + 1);//后一行像素的指针        uchar* output = Result.ptr<uchar>(j);        for(int i= nChannels;i < nChannels*(myImage.cols-1); ++i)        {            *output++ = saturate_cast<uchar>(5*current[i]                         -current[i-nChannels] - current[i+nChannels] - previous[i] - next[i]);        }    }    Result.row(0).setTo(Scalar(0));    Result.row(Result.rows-1).setTo(Scalar(0));    Result.col(0).setTo(Scalar(0));    Result.col(Result.cols-1).setTo(Scalar(0));}

运行结果：

程序解释见：

http://www.opencv.org.cn/opencvdoc/2.3.2/html/doc/tutorials/core/mat-mask-operations/mat-mask-operations.html#maskoperationsfilter