如何使用Python和OpenCV从目录中读取图像？

Question

I wrote the following code:

import os
import cv2
import random
from pathlib import Path

path = Path(__file__).parent
path = "../img_folder"
for f in path.iterdir():

    f = str(f)

    img=cv2.imread(f)

    im_height = img.shape[0]
    im_width = img.shape[1]

But when I run this code, I get the following error:

AttributeError: 'NoneType' object has no attribute 'shape' in im_height = img.shape[0].

I think I cannot access images, so I wrote print(img) and print(type(omg)) and None& is returned. img_folder is a folder that has 10 images. When I print out f , I get:

../img_folder/.DS_Store

I do not know why .DS_Store is contained because img_folder has only images. How should I fix this? What should I write this? Why can't I access images?

Answer 1

You have post at least three questions about get filenames with "PostPath". Badly.

A better way is use glob.glob to get the specific type of filenames.

$ tree .
├── a.txt
├── feature.py
├── img01.jpg
├── img01.png
├── imgs
│   ├── img02.jpg
│   └── img02.png
├── tt01.py
├── tt02.py
└── utils.py

1 directory, 9 files

From current directory:

import glob
import itertools

def getFilenames(exts):
    fnames = [glob.glob(ext) for ext in exts]
    fnames = list(itertools.chain.from_iterable(fnames))
    return fnames


## get `.py` and `.txt` in current folder
exts = ["*.py","*.txt"]
res = getFilenames(exts)
print(res)
# ['utils.py', 'tt02.py', 'feature.py', 'tt01.py', 'a.txt']


# get `.png` in  current folder and subfolders
exts = ["*.png","*/*.png"]
res = getFilenames(exts)
print(res)
# ['img01.png', 'imgs/img02.png']

Answer 2

The .DS_Store file is a kind of hidden file, which is automatically generated (only on Mac OS), inside the various directories, which you may have opened using the Finder application. I guess it is some sort of cache file for fast and easy rendering of directory structure in the Finder . I have observed that it doesn't gets created if I do not open the directory with my Finder application.

To prevent this sort of errors, you must always check that the file you are going to read has a valid extension. It can be done as:

import os

for file_name in os.listdir("/path/to/your/directory"):
    if file_name.split(".")[-1].lower() in {"jpeg", "jpg", "png"}:
        img = cv2.imread("/path/to/your/directory/" + file_name)

Answer 3

It is because of a hidden file in your directory. If you are sure your directory contains only images, you can ignore hidden files/folders like below.

use

for f in path.iterdir():
    if not f.startswith('.'):

      f = str(f)

      img=cv2.imread(f)

      im_height = img.shape[0]
      im_width = img.shape[1]