How to access or detect a length of object/s in openCV?

Question

I am just new to openCV(3 days old) and currently creating a project that should assign different amounts of time for different lengths detected.

I was just wondering if there's a way to analyze or to run though the Y-axis of an image and then detect the presence(first binary 1 detected) and the end of an object or end of the length( last binary 1 detected after 0). I am having a hard time coding such using openCV since I don't know how openCV assigns X and Y axis in the digital image.

here is the picture binaryimage

Is there a way to know the area? or length of such objects?

Answer 1

To assign a pixel value for a cv::Mat image:

• For grayscale image ( 8UC1 )

   img.at<uchar>(y, x) = (uchar) value; 

• For Color image ( BGR style)

   img.at<Vec3b>(y, x) = Vec3b(blueValue, greenValue, redValue);