I am having a object of image declared as Mat img; now how to get the address of zeroth row and zeroth column in memory
in what datatype it will be? how many bytes it takes to store value in one single cell of matrix?
You can directly access data at the address Mat::datastart
You should read that : http://docs.opencv.org/modules/core/doc/basic_structures.html?highlight=datastart#mat
For an image, data is stored row by row. You should also consider using Mat::at<type>(y,x).
Every Mat object has an pointer to its data, for example with Mat img; the data pointer is img.data. Based on your image type (when declaring or reading from image file), that pointer can be casted to unsigned char * (for CV_8U or CV_8UC1, grayscale image and other CV_8Uxx), float * (for CV_32F and other CV_32FCxx), double * (for CV_64F or other CV_64Fxx). Based on your image datatype, you will know how many bytes it needs to store a single cell.
let us take image is CV_32F Mat img; float * data ; data= ??? i want to access value in the first cell of a matrix how to do that
Mat img; ... <do some works with img> float * pImg = (float*)img.data;
then pImg[0] is the first cell, the first row will end at pImg[img.cols-1]. You can access all cells with indexes range from 0 to (img.rows*img.cols)-1. Please mark your question as answered when you find what you want.
Asked: 2014-02-20 07:36:49 -0600
Seen: 1,137 times
Last updated: Feb 20 '14
