Is opencv matrix data guaranteed to be continuous?

Question

I know that, the data contained in an opencv matrix is not guaranteed to be continuous. To make myself clear, here is a paragraph from Opencv documentation:

Answer 1

Data stored in OpenCV cv::Mats are not always continuous in memory, which can be verified via API Mat::isContinuous(). Instead, it follows the following rules:

1. Matrices created by imread(), clone(), or a constructor will always be continuous.
2. The only time a matrix will not be continuous is when it borrows data from an existing matrix (i.e. created out of an ROI of a big mat), with the exception that the data borrowed is continuous in the big matrix, including
   • borrow a single row;
   • borrow multiple rows but with full original width.

The following code from my blog demonstrates this in a better way (see the inline comments for further explanation).

std::vector mats(7);

// continuous as created using constructor
mats[0] = cv::Mat::ones(1000, 800, CV_32FC3);      

// NOT continuous as borrowed data is not continuous (multiple rows and not full original width)
mats[1] = mats[0](cv::Rect(100, 100, 300, 200));     

// continuous as created using clone()
mats[2] = mats[1].clone();               

// continuous for single row always    
mats[3] = mats[2].row(10);             

// NOT continuous as borrowed data is not continuous (multiple rows and not full original width)         
mats[4] = mats[2](cv::Rect(5, 5, 100, 2));     

// continuous as borrowed data is continuous (multiple rows with full original width)   
mats[5] = mats[2](cv::Rect(0, 5, mats[2].cols, 2));

// NOT continuous as borrowed data is not continuous (multiple rows and not full original width) 
mats[6] = mats[2].col(10);