How To Get A Contour Of More/Less Of The Expected Area In OpenCV Python

July 21, 2022 Post a Comment

I doing some contour detection on a image and i want to find a contour based on a area that i will fix in this case i want the contour marked in red. So i want a bounding box aroun

Solution 1:

import cv2
import numpy as np
#EDIT: imutils to grab contours
import imutils

def nothing(x):
    pass
'''
cv2.namedWindow("Tracking")
cv2.createTrackbar("LH", "Tracking", 0, 255, nothing)
cv2.createTrackbar("LS", "Tracking", 0, 255, nothing)
cv2.createTrackbar("LV", "Tracking", 0, 255, nothing)
cv2.createTrackbar("UH", "Tracking", 255, 255, nothing)
cv2.createTrackbar("US", "Tracking", 255, 255, nothing)
cv2.createTrackbar("UV", "Tracking", 255, 255, nothing)
'''

frame = cv2.imread('so.jpg')
img = frame.copy()

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

l_h = cv2.getTrackbarPos("LH", "Tracking")
l_s = cv2.getTrackbarPos("LS", "Tracking")
l_v = cv2.getTrackbarPos("LV", "Tracking")

u_h = cv2.getTrackbarPos("UH", "Tracking")
u_s = cv2.getTrackbarPos("US", "Tracking")
u_v = cv2.getTrackbarPos("UV", "Tracking")

l_b = np.array([65, 0, 28])
u_b = np.array([120, 120, 130])

mask = cv2.inRange(hsv, l_b, u_b)

res = cv2.bitwise_and(frame, frame, mask=mask)
res1 = res.copy()

res = cv2.cvtColor(res,cv2.COLOR_BGR2GRAY)

cont = cv2.findContours(res,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)
#EDIT: I CAN'T REALLY REMEMBER WHAT IT DOES, BUT IT IS WORKING..
cont = imutils.grab_contours(cont)

closed_contours = []
open_contours = []

for count,i in enumerate(cont):
    #EDIT:produce boxes out of contours found before computing countourArea
    rect = cv2.minAreaRect(i)
    box = cv2.boxPoints(rect)
    i = np.int0(box)
    
    #HINT:IMPROVE THIS CONDITIONS. IT IS BASED ON FILTERING THE OTHER BOXES APPEARED..
    if (cv2.contourArea(i) < 2000 and cv2.contourArea(i)>100):#cv2.arcLength(i, True):
        print(cv2.contourArea(i))
        closed_contours.append(i)

#EDIT:(0,0,255) made box appeared in red color
cont_img = cv2.drawContours(img, closed_contours, -1, (0,0,255), 3)
c = max(closed_contours, key=cv2.contourArea)
x, y, w, h = cv2.boundingRect(c)

#EDIT: REMOVED CODE OUT OF WHILE- IT S NOT A VIDEO TO GRAB CONCURRENT FRAMES
while True:
    #cv2.imshow("frame", frame)
    #cv2.imshow("mask", mask)
    #cv2.imshow("res", res1)
    cv2.imshow("img",cont_img)

    key = cv2.waitKey(1)
    if key == 27:
        break

cv2.destroyAllWindows()