C++ 中 opencv Mat 变量的常见运算

1. cv::Mat 的属性 

cv::Mat img ;

img = cv::imread( img_path, CV_LOAD_IMAGE_COLOR ) ;

if ( !img.data )

    std::cout << "Could not open or find file " << img_path << std::endl ;

int img_rows =  img.rows ; Mat 的高宽属性

int img_cols = img.cols ;

for( int h; h<img_rows; h++)

     for( int w; w<img_cols; w++ )

       {

        img.at<uchar>(h, w ) ; note the order of the height and cols

       }                                         similar as that of matlab. 

 cv::Mat img( height, width, CV_8UC1, cv::Scalar(0) ) ;

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cv::Rect roi ;

roi.x = 0 ;  start index of width 

roi.y = 0 ; start index of height

roi.width = (int) img_cols/2 ; 

roi.height = (int) img_rows/2 ;

cv::Mat crop_img ;

img(roi).copyTo(crop_img) ;   切取图像块

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int crop_size_w = (int) img_cols/4 ;

int crop_size_h = (int)img_rows/4 ;

cv::Size inputSize( crop_size_w, crop_size_h  ) ; note the order ???

cv::resize( crop_img, crop_img, inputSize, 0, 0, cv::INTER_LINEAR ) ;

resize image.   ( src, dst, dst.size(),  ... )

/// resize(src, dst, dst.size(), 0, 0, interpolation);

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int do_mirror = 1 ;

if( do_mirror )

    cv::flip( crop_img, crop_img, 1 ) ;  / 图像镜像

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---以上内容为个人观点，仅供参考。