Getting the x and y coordinates from cv2.contour in Open CV Python and store it to different variables

Question

I'm printing the contour from cv2.findContours. It prints out something like these: [[370 269]] What i want is to get the 370 and store it into a variable.

import cv2
import numpy as np
cap = cv2.VideoCapture(0)

while True:
    _, frame = cap.read()


    hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

    lower = np.array([0,0,255]) 
    upper = np.array([255,255,255])

    imgThreshHigh = cv2.inRange(hsv, lower, upper)
    thresh = imgThreshHigh.copy()

    _,contours,_ = cv2.findContours(thresh, 
                cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

    print(contours)

    cv2.imshow('frame',frame)
    cv2.imshow('Object',thresh)
    k = cv2.waitKey(5) & 0xFF
    if k == 27:
        break
cv2.destroyAllWindows()

Answer 1

Do you know destructuring ?

data = [370, 269]
x, y = data

print(x)
# 370

print(y)
#269

Or, if data is a list of list:

data = [[370, 269]]
[[x, y]] = data

print(x)
# 370

print(y)
#269

Answer 2

This might be late for you, I guess it will help someone. To get the x, y value of a contour I used this

for contour in contours:
    x, y, _, _ = cv2.boundingRect(contour)
    print(x, " ", y)

This gets the x, y coordinates of the starting point of the contour. The two underscores are width and height, ignored as we don't need them.

Answer 3

I worked out the following for storing all x and y coordinates for a single contour:

x = []
y = []
for k in contours:
    for i in k:
        for j in i:
            x.append(j[0])
            y.append(j[1])

I am sure there must be a faster way !!

Answer 4

kx = contours[k][:,0,0]
ky = contours[k][:,0,1]

Answer 5

Here is a function I wrote to write the coordinates into a nested list. The list contains as many lists as contours. Each individual list hosts a list of XY coordinate of the contour.

def get_xy_list_from_contour(contours):
    full_dastaset = []
    for contour in contours:
        xy_list=[]
        for position in contour:
            [[x,y]] = position
            xy_list.append([x,y])
        full_dastaset.append(xy_list)
    return full_dastaset