python - Python 中的名称错误

Question

尝试在 cmd 上运行 Python 中的 OpenCV 项目时，我遇到了 NameError: name 'eyes' not found。我正在使用 Python 2.7 和 OpenCV 2.4.13，我认为这不是问题。

import cv2
import numpy as np

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

eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')

cap = cv2.VideoCapture(1)

while True:
    ret, img = cap.read()
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    faces = face_cascade.detectMultiScale(gray, 1.3, 5)
    for(x,y,w,h) in faces:
        cv2.reactangle(img, (x,y), (x+w,y+h), (255,0,0), 2)
        roi_gray = gray[y:y+h, x:x+w]
        roi_color = img[y:y+h, x:x+w]
        eyes = eye_cascade.detectMultiScale(roi_gray)
    for(ex,ey,ew,eh) in eyes:
        cv2.rectangle(roi_color, (ex, ey), (ex+ew,ey+eh), (0,255,0), 2)

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

cap.release()
cv2.destroyAllWindows() 

错误:

File "detect.py" , line 19, in
for(ex,ey,ew,eh) in eyes:
NameError: name 'eyes' is not defined

Answer 1

缩进问题，就像this one :

当您离开 faces 循环时，

eyes 超出范围。

while True:
    ret, img = cap.read()
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    faces = face_cascade.detectMultiScale(gray, 1.3, 5)
    for(x,y,w,h) in faces:
        cv2.reactangle(img, (x,y), (x+w,y+h), (255,0,0), 2)
        roi_gray = gray[y:y+h, x:x+w]
        roi_color = img[y:y+h, x:x+w]
        eyes = eye_cascade.detectMultiScale(roi_gray)
        # this one should be inside the 'faces' loop
        for(ex,ey,ew,eh) in eyes:
            cv2.rectangle(roi_color, (ex, ey), (ex+ew,ey+eh), (0,255,0), 2)

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