Question

我正在使用连接到Raspberry Pi 2型号B的网络摄像头拍摄照片。然后，我检测到照片中的脸部并裁剪脸部并将其另存为单独的图像。以下代码在Windows中完美运行。

import numpy as np
import cv2
import math
from random import random

face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
cap = cv2.VideoCapture(0)
ret,frame = cap.read()

#naming the image and save path

img_name = str(int(math.ceil(100000*random())))
img_path = 'images/'+img_name+'.png'
crop_img_path = 'images/'+'crop_'+img_name+'.png'

# directly saving the image
cv2.imwrite(img_path,frame)

cap.release()

img = cv2.imread(img_path)  #read image to numeric array

#printing image information
print str(img.shape) + " "
print str(img.size) + " "
print str(img.dtype)

#detecting face
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
face_cascade.load('haarcascade_frontalface_default.xml')
faces = face_cascade.detectMultiScale(gray, 1.3, 5)
for (x,y,w,h) in faces:
    img = cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2) # drawing rectangle (Blue, thickness 2)
    print str(x)+" "+str(y)+" "+str(x+w)+" "+str(y+h) #printing region coordinates of rectangle
    crop_img = img[y:y+h,x:x+w]
    cv2.imwrite(crop_img_path,crop_img)

但它在Raspbian中给出了以下错误：

Traceback (most recent call last):
File "xyz.py", line 35, in <module>
crop_img = img[y:y+h,x:x+w]
TypeError: 'NoneType' object has no attribute '__getitem__'

注1：原始拍摄的图像保存在images文件夹中。

注2：我使用follow命令安装了OpenCV for Python：

sudo apt-get install python-opencv

Answer 1

你的问题就在这一行： img = cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2)此处您将img重新分配给None，以免丢失原始对象。

参考OpenCV2 documentation，cv2.rectangle返回None。

因此，

crop_img = img[y:y+h,x:x+w]会显示错误消息

矩形

绘制一个简单，厚实或填充右上方的矩形。

C ++：void rectangle（Mat＆amp; img，Point pt1，Point pt2，const Scalar＆amp;   color，int thickness = 1，int lineType = 8，int shift = 0）

C ++：void rectangle（Mat＆amp; img，Rect rec，const Scalar＆amp; color，int   thickness = 1，int lineType = 8，int shift = 0）

Python：cv2.rectangle（img，pt1，pt2，color [，thickness [，lineType [，   shift]]]）→无

C：void cvRectangle（CvArr * img，CvPoint pt1，CvPoint pt2，CvScalar   color，int thickness = 1，int line_type = 8，int shift = 0）

Python：cv.Rectangle（img，pt1，pt2，color，thickness = 1，lineType = 8，   shift = 0）→无

为了修复您的代码，您不应该重新分配img，而应该执行以下操作：

for (x,y,w,h) in faces:
    cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2) # drawing rectangle (Blue, thickness 2)
    print str(x)+" "+str(y)+" "+str(x+w)+" "+str(y+h) #printing region coordinates of rectangle
    crop_img = img[y:y+h,x:x+w]
    cv2.imwrite(crop_img_path,crop_img)

在Raspbian上裁剪图像OpenCV 2

1 个答案: