Python3 'cv2.resizeWindow('img', 500,500)' 错误

Question

我正在尝试运行这个面部跟踪程序提供 here，但是运行宁 python 程序 returns;

Traceback (most recent call last):
  File "C:\Users\User\Desktop\Projects\Face Tracking\servo\face.py", line 27, in <module>
    cv2.resizeWindow('img', 500,500)
cv2.error: OpenCV(4.5.5) D:\a\opencv-python\opencv-python\opencv\modules\highgui\src\window_w32.cpp:1473: error: (-27:Null pointer) NULL window: 'img' in function 'cvResizeWindow'

我使用以下命令安装了 OpenCV：python3 -m pip install opencv-python。

这是完整的代码。

"""
   *Face Tracking System Using Arduino - Python Code*
    Close the Arduino IDE before running this code to avoid Serial conflicts.
    Replace 'COM5' with the name of port where you arduino is connected.
    To find the port check Arduino IDE >> Tools >> port.
    Upload the Arduino code before executing this code.

    # Code by Harsh Dethe, 09 Sep 2018 #
"""
import numpy as np
import serial
import time
import sys
import cv2

arduino = serial.Serial('COM3', 9600)
time.sleep(2)
print("Connection to arduino...")


face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

cap = cv2.VideoCapture(0)

while 1:
    ret, img = cap.read()
    cv2.resizeWindow('img', 500,500)
    cv2.line(img,(500,250),(0,250),(0,255,0),1)
    cv2.line(img,(250,0),(250,500),(0,255,0),1)
    cv2.circle(img, (250, 250), 5, (255, 255, 255), -1)
    gray  = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    faces = face_cascade.detectMultiScale(gray, 1.3)

    for (x,y,w,h) in faces:
        cv2.rectangle(img,(x,y),(x+w,y+h),(0,255,0),5)
        roi_gray  = gray[y:y+h, x:x+w]
        roi_color = img[y:y+h, x:x+w]

        arr = {y:y+h, x:x+w}
        print (arr)
        
        print ('X :' +str(x))
        print ('Y :'+str(y))
        print ('x+w :' +str(x+w))
        print ('y+h :' +str(y+h))

        xx = int(x+(x+h))/2
        yy = int(y+(y+w))/2

        print (xx)
        print (yy)

        center = (xx,yy)

        print("Center of Rectangle is :", center)
        data = "X{0:d}Y{1:d}Z".format(xx, yy)
        print ("output = '" +data+ "'")
        arduino.write(data)
    

    cv2.imshow('img',img)
   
    k = cv2.waitKey(30) & 0xff
    if k == 27:
        break

Answer 1

错误是：

error: (-27:Null pointer) NULL window: 'img' in function 'cvResizeWindow'

这意味着 给定的 window 不存在 （还）。

您应该首先使用 createWindow 或 imshow 创建 window。

A window 不是图像。包含某事物名称的字符串 ("img") 不是事物 (img)。如果你想 resize() 图像，你使用了错误的函数。

Answer 2

检查这个希望它有用！

   """
   *Face Tracking System Using Arduino - Python Code*
    Close the Arduino IDE before running this code to avoid Serial conflicts.
    Replace 'COM5' with the name of port where you arduino is connected.
    To find the port check Arduino IDE >> Tools >> port.
    Upload the Arduino code before executing this code.

    # Code by Harsh Dethe, 09 Sep 2018 #
"""
import numpy as np
import serial
import time
import sys
import cv2

arduino = serial.Serial('COM3', 9600)
time.sleep(2)
print("Connection to arduino...")


face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

cap = cv2.VideoCapture(0)

while 1:
    ret, img = cap.read()
    if ret == True:
        cv2.namedWindow("img", cv2.WINDOW_NORMAL)
        cv2.resizeWindow('img', 500, 500)
        cv2.line(img, (500, 250), (0, 250), (0, 255, 0), 1)
        cv2.line(img, (250, 0), (250, 500), (0, 255, 0), 1)
        cv2.circle(img, (250, 250), 5, (255, 255, 255), -1)
        gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
        faces = face_cascade.detectMultiScale(gray, 1.3)

        for (x, y, w, h) in faces:
            cv2.rectangle(img, (x, y), (x+w, y+h), (0, 255, 0), 5)
            roi_gray = gray[y:y+h, x:x+w]
            roi_color = img[y:y+h, x:x+w]

            arr = {y: y+h, x: x+w}
            print(arr)

            print('X :' + str(x))
            print('Y :'+str(y))
            print('x+w :' + str(x+w))
            print('y+h :' + str(y+h))

            xx = int(x+(x+h))/2
            yy = int(y+(y+w))/2

            print(xx)
            print(yy)

            center = (xx, yy)

            print("Center of Rectangle is :", center)
            data = "X{0:d}Y{1:d}Z".format(xx, yy)
            print("output = '" + data + "'")
            arduino.write(data)

        cv2.imshow('img', img)

        k = cv2.waitKey(30) & 0xff
        if k == 27:
            break
    else:
        break

Answer 3

更简单的方法。在 while 条件块之前总是使用 nameWindow。很实用的方法，防止出错。

# Naming a window
cv2.namedWindow("img", cv2.WINDOW_NORMAL)
while 1:
    ret, img = cap.read()
    cv2.resizeWindow('img', 500,500)

Python3 'cv2.resizeWindow('img', 500,500)' 错误

Python3 'cv2.resizeWindow('img', 500,500)' error

python

opencv

image-processing