我使用python和opencv3在實時流上繪制了最大的圖像輪廓，看起來我的代碼出錯了，有人可以幫我嗎

Question

我使用python和opencv3在實時流上繪制了最大的圖像輪廓，看起來我的代碼出錯了，有人可以幫我嗎

import cv2,platform
import numpy as np

def larger(x):
    gray = cv2.cvtColor(x, cv2.COLOR_BGR2GRAY)
    image = cv2.Canny(gray,35,200)
    (_,cnts,_) = cv2.findContours(image.copy(), cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
    c = max(cnts, key=cv2.contourArea)
    return cv2.minAreaRect(c)
capture = cv2.VideoCapture(0)
retval, im = capture.read()
y = larger(im)
box = np.int0(cv2.boxPoints(y))
cv2.drawContours(im,[box],-1,(0,255,0),2)
cv2.imshow("Image",im)
cv2.waitKey(0)
cv2.destroyAllWindows()

我有此代碼的兩個問題：

1) is my web cam was on but cant see any video image, getting this error

    "Traceback (most recent call last):
      File "C:\Users\Snehith\Desktop\project vision\cnt.py", line 14, in <module>
        y = larger(im)
      File "C:\Users\Snehith\Desktop\project vision\cnt.py", line 8, in larger
        c = max(cnts, key=cv2.contourArea)
    ValueError: max() arg is an empty sequence"
2) i want a continuous video stream along with the contour, please explain the mistakes and also solutions in python and opencv 

Answer 1

我只需要對您的代碼做兩個小改動：

1.）您可以檢查capture.isOpened（）以查看是否連接了攝像機。

2.）我包含一個while循環，以便您連續拉動幀，直到按下'q'。

import cv2,platform
import numpy as np

def larger(x):
    gray = cv2.cvtColor(x, cv2.COLOR_BGR2GRAY)
    image = cv2.Canny(gray,35,200)
    (_,cnts,_) = cv2.findContours(image.copy(), cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
    c = max(cnts, key=cv2.contourArea)
    return cv2.minAreaRect(c)

capture = cv2.VideoCapture(0)

if capture.isOpened():
    while(True):
        retval, im = capture.read()
        y = larger(im)
        box = np.int0(cv2.boxPoints(y))
        cv2.drawContours(im,[box],-1,(0,255,0),2)
        cv2.imshow("Image",im)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            capture.release()
            break

else:
    print "No camera detected."


cv2.destroyAllWindows()    

您可能會發現OpenCV Python教程對類似的問題有所幫助，這是pdf版本的鏈接： https : //media.readthedocs.org/pdf/opencv-python-tutroals/latest/opencv-python-tutroals.pdf