How to draw a line in OpenCV using C++?

To draw a line we need two points-the starting point and ending point. We also require a canvas to draw the line.

Using OpenCV, the matrix in our canvas, we need to define the line's starting and ending points. We require to assign a color to the line as well. The thickness of the line has to be explained too. If we want to draw a line using OpenCV, we need to declare a matrix, two points, and color and line thickness.

Using OpenCV we have to include header because line() function is defined in this header.

The basic syntax of this method is as follows −

Syntax

line(whiteMatrix, starting, ending, line_Color, thickness);

The following program shows how to draws a line on an image in OpenCV −

Example

#include
#include
#include
using namespace cv;
using namespace std;
int main() {
   Mat whiteMatrix(200, 200, CV_8UC3, Scalar(255, 255, 255));//Declaring a white matrix//
   Point starting(50, 50);//Starting Point of the line
   Point ending(150, 150);//Ending Point of the line
   Scalar line_Color(0, 0, 0);//Color of the line
   int thickness = 2;//thickens of the line
   namedWindow("GrayImage");//Declaring a window to show the line
   line(whiteMatrix, starting, ending, line_Color, thickness);//using line() function to draw the line//
   imshow("GrayImage", whiteMatrix);//showing the line//
   waitKey(0);//Waiting for KeyStroke
   return 0;
}

Output