how can i read a greyimage line by line opencv c++ - c++

Question

I have a grey image ,i want to read every line from the image .
how can i do this algorithm ?
can anyone help me
there is the code what im using
//#include "stdafx.h"
#include <stdio.h>
#include <cv.h>
#include <iostream>
#include <conio.h>
#include <cxcore.h>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <stdlib.h>
using namespace cv;
Mat dst;
void main()
{
cv::Mat img = cv::imread("capture.jpg",CV_LOAD_IMAGE_GRAYSCALE);
cv::Mat some_row = img.row(0); //gives 1st row
namedWindow( "source",CV_NORMAL);
imshow( "source",img);
namedWindow( "img",CV_NORMAL);
imshow( "img",dst);
waitKey(0);
from the image i like to sort the color and make a test if i can found the order white color then black end then white and then black .
for this reason i like to make a search row by row.
i can share the picture that you can more understand me .
i have make an algorithm who can detect the circle from the right and the left side
and that works.I need a code who search only the color and no object from the image (color in order (White.Black.White.Black) to get the right position what im searching)
us im shown in image .https://drive.google.com/file/d/0B1WQBCaQu10geG1uTm40ZG9IVjQ/edit?usp=sharing

Answer 1

I suggest that you read the opencv tutorial on scanning images. You should also have a look at the documentation for the Mat class.
There is more than one way of doing what you need. Different methods have different efficiency and safety trade offs. More efficient methods work directly with pointers. This is fast, but you must take care of doing pointer arithmetics right depending of the number of pixels, channels and padding your image may have stored in memory.
On the other hand, using an iterator or even something like Mat::at is safer since these calculations are made for you. But it isn't as efficient.
Have a look at the documentation and choose what is right for your problem. Hope that helps.

Answer 2

You can use .row() method:
cv::Mat img = cv::imread("some_path.jpg",CV_LOAD_IMAGE_GRAYSCALE);//some gray level image
cv::Mat some_row = img.row(0); //gives 1st row
Note that this method causes data sharing with the original matrix img. If you want to have a copy operation, you can use .copyTo() method.