How to read images from a directory with Python and OpenCV?

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?

You would have to provide us more information. print f and post the output. And if the folder does not contain a lot of images, why not just use os.listdir ? — Ganesh Tata
– Ganesh Tata, Commented Dec 28, 2017 at 5:19
@GaneshTata, there's plenty of information: they're a macOS user, and do not know about hidden files (like .DS_Store), and how macOS stores .DS_Store files in every directory for settings by default. To the OP, you should filter only for images matching a glob pattern, for example, *.jpg. — Alex Huszagh
– Alex Huszagh, Commented Dec 28, 2017 at 5:22

Kinght 金 · Accepted Answer · 2017-12-28 06:11:06Z

5

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']

edited Dec 28, 2017 at 6:11

answered Dec 28, 2017 at 5:28

Kinght 金

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2 Comments

user8817674 Over a year ago

thx ur answer.How should I get purpose file(image) by using if statement?

Kinght 金 Over a year ago

@user8817674 for example? what if statement do you want?

ZdaR · Accepted Answer · 2017-12-28 05:34:44Z

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)

Prakash Palnati · Accepted Answer · 2017-12-28 05:23:42Z

1

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]

answered Dec 28, 2017 at 5:23

Prakash Palnati

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4 Comments

Alex Huszagh Over a year ago

A good solution in the future would be to use the glob module, rather than pathlib, to match only files with a desired extension. For example, glob.glob('*.jpg'), as this would work with directories containing extraneous data.

user8817674 Over a year ago

@Prakash thx ur answer.I wrote ur codes,but nothing can be gotten.It means the number of img is 0.What is wrong?

Prakash Palnati Over a year ago

print all f before doing anything right after for loop. you will get some clue.

user8817674 Over a year ago

@PrakashPalnati f is ` ../img_folder/.DS_Store` & ../img_folder/01.png ・・・.I can understand why nothing is gotten.But how should I fix this?

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