Why the function cv2.HoughLinesP() has different effects?

Question

I learn in this link.

This is the original picture：

My test code:

import cv2
import numpy as np

img = cv2.imread( 'E:/image/sudoku.png' )
gray = cv2.cvtColor( img,cv2.COLOR_BGR2GRAY )
edges = cv2.Canny( gray,50,150,apertureSize = 3 )
minLineLength = 100
maxLineGap = 10
lines = cv2.HoughLinesP( edges,1,np.pi/180,100,minLineLength,maxLineGap )
for line in lines:
    for x1,y1,x2,y2 in line:
        cv2.line( img,( x1,y1 ),( x2,y2 ),( 0,255,0 ),2 )
cv2.imwrite( 'E:/image/myhoughlinesp.jpg',img )
cv2.imshow( '1',img )
cv2.waitKey(0)

The result of my code running：

But the picture generated by the official website is like this：

If you don't change the code.(Use that link's code),the generated picture is like this:

When I change the code, although there are a lot of green lines,but doesn't have the official website's good effect.

Why do I have a different picture from the official website?

Answer 1

I know why the effect is different.

The function cv2.HoughLinesP() in python3.X has 7 parameters.

def HoughLinesP(image, rho, theta, threshold, lines=None, minLineLength=None, maxLineGap=None):

But the code of the official website only writes 6 parameters.So you should write the name of the parameter,like this:

import cv2
import numpy as np

img = cv2.imread( 'E:/image/sudoku.png' )
gray = cv2.cvtColor( img,cv2.COLOR_BGR2GRAY )
edges = cv2.Canny( gray,50,150,apertureSize = 3 )
minLineLength = 100
maxLineGap = 10
lines = cv2.HoughLinesP( edges,1,np.pi/180,100,minLineLength=minLineLength,maxLineGap=maxLineGap )
for line in lines:
    for x1,y1,x2,y2 in line:
        cv2.line( img,( x1,y1 ),( x2,y2 ),( 0,255,0 ),2 )
cv2.imwrite( 'E:/image/myhoughlinesp.jpg',img )
cv2.imshow( '1',img )
cv2.waitKey(0)

Result picture: