python OpenCV, draw grid example source code

make well divided linear coordinate
And make pair coordinate

Please see code for detail explanation.

import numpy as np

import cv2

import sys

rows = 500

cols = 500

newMat_3ch = np.zeros((rows, cols, 3), dtype = "uint8") #3channel

step = 20

x = np.linspace(start=0, stop=rows, num=step)

y = np.linspace(start=0, stop=cols, num=step)

v_xy = []

h_xy = []

for i in range(step):

v_xy.append( [int(x[i]), 0, int(x[i]), rows-1] )

h_xy.append( [0, int(y[i]), cols-1, int(y[i])] )

for i in range(step):

[x1, y1, x2, y2] = v_xy[i]

[x1_, y1_, x2_, y2_] = h_xy[i]

cv2.line(newMat_3ch, (x1,y1), (x2, y2), (0,0,255),1 )

cv2.line(newMat_3ch, (x1_,y1_), (x2_, y2_), (255,0,0),1 )

cv2.namedWindow('newMat_3ch',0)

cv2.imshow('newMat_3ch', newMat_3ch)

cv2.waitKey(0)

OpenCV, Dash line drawing example source code.

I can know all coordinate from A point to B point using "LineIterator" function in OpenCV.
So this source code is applied by this "LineIterator".


..

Mat DrawDashLine(Mat inMat, Point start, Point end, int gap, Scalar color)
{
    Mat rMat;
    rMat = inMat.clone();
    
    cv::LineIterator it(rMat, start, end, 8);
    vector< pair<cv::Point, cv::Point> > vecPt_pair;
    vector< cv::Point > vecPt;

    Point A, B;
    A = start;
    for (int i = 0, j = 0; i < it.count; i++, it++)
    {
        
        if (i % gap == 0)
        {
            //update end point
            B = it.pos();

            if(j%2)
                line(rMat, A, B, color, 2);

            //update start point
            A = B;
            j++;
        }
    }

    return rMat;
}

int main()
{
    Mat img(500, 500, CV_8UC3);
    img.setTo(0);

    Mat rImg = DrawDashLine(img, Point(20, 20), Point(300, 300), 10, CV_RGB(255, 0, 0));

    namedWindow("test", 0);
    cv::imshow("test", rImg);
    waitKey(0);
    
    return 0;
}

..