How to use `cv2.findContours` in different OpenCV versions?
15,483
An alternative to work with 2.x 、3.x、4.x is:
cnts, hiers = cv2.findContours(...)[-2:]
Notice:
cv2.findContours
has changed since OpenCV 3.x
, but in OpenCV 4.0
it changes back!!!
In OpenCV 3.4:
findContours(image, mode, method[, contours[, hierarchy[, offset]]]) -> image, contours, hierarchy
In OpenCV 4.0:
findContours(image, mode, method[, contours[, hierarchy[, offset]]]) -> contours, hierarchy
Author by
DSmith
Updated on June 17, 2022Comments
-
DSmith about 2 years
I am trying to use OpenCV with Python in order to detect squares in a live video feed from a Raspberry Pi camera. However, the
cv2.GaussianBlur
andcv2.Canny
functions in the code below are causing the following error: "TypeError: numpy.ndarray' object is not callable".I cannot seem to resolve the error. Any help is appreciated.
import cv2 # load the video camera = cv2.VideoCapture(0) # keep looping while True: # grab the current frame and initialize the status text (grabbed, frame) = camera.read() status = "No Targets" # check to see if we have reached the end of the # video if not grabbed: break # convert the frame to grayscale, blur it, and detect edges gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) blurred = cv2.GaussianBlur(gray, (7, 7), 0) edged = cv2.Canny(blurred, 50, 150) # find contours in the edge map (cnts, _) = cv2.findContours(edged.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE) # loop over the contours for c in cnts: # approximate the contour peri = cv2.arcLength(c, True) approx = cv2.approxPolyDP(c, 0.01 * peri, True) # ensure that the approximated contour is "roughly" rectangular if len(approx) >= 4 and len(approx) <= 6: # compute the bounding box of the approximated contour and # use the bounding box to compute the aspect ratio (x, y, w, h) = cv2.boundingRect(approx) aspectRatio = w / float(h) # compute the solidity of the original contour area = cv2.contourArea(c) hullArea = cv2.contourArea(cv2.convexHull(c)) solidity = area / float(hullArea) # compute whether or not the width and height, solidity, and # aspect ratio of the contour falls within appropriate bounds keepDims = w > 25 and h > 25 keepSolidity = solidity > 0.9 keepAspectRatio = aspectRatio >= 0.8 and aspectRatio <= 1.2 # ensure that the contour passes all our tests if keepDims and keepSolidity and keepAspectRatio: # draw an outline around the target and update the status # text cv2.drawContours(frame, [approx], -1, (0, 0, 255), 4) status = "Target(s) Acquired" # draw the status text on the frame cv2.putText(frame, status, (20, 30), cv2.FONT_HERSHEY_SIMPLEX, 0.5, (0, 0, 255), 2) # show the frame and record if a key is pressed cv2.imshow("Frame", frame) key = cv2.waitKey(1) & 0xFF # if the 'q' key is pressed, stop the loop if key == ord("q"): break # cleanup the camera and close any open windows camera.release() cv2.destroyAllWindows()