cv2.imwrite 不保存图像

Question

i've an issue with cv2.imiwrite

there are two folders, the photos is for normal image then the gray is folder to save the grayscale image from normal photo that already changed

i want to read a normal image and change to grayscale, and then save the grayscale

so this is my code

import cv2
import os 
import glob

count = 0

os.chdir('./photos')
for file in glob.glob('*.jpg'):
    image = cv2.imread(file)
    image_gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    cv2.imwrite('./gray/grayscale{}.jpg'.format(count), image_gray)
    count += 1

the image = cv2.imread(file) have an array, and so the image_gray = cv2.cvtColor(image, cv2.COLORBGR2GRAY) have and array too. but why my cv2.imwrite code not saving the grayscale image to folder? i've searched answer in this forum but none of them answer my question. any answer would be appreciated. thanks in advance !

Answer 1

Please, don't do this, especially chdir() etc.:

os.chdir('./photos')
for file in glob.glob('*.jpg'):
    image = cv2.imread(file)
    image_gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    cv2.imwrite('./gray/grayscale{}.jpg'.format(count), image_gray)
    count += 1

Instead you may use much easier:

if not os.path.isdir( 'gray' ) :
    os.mkdir( 'gray' )  # make sure the directory exists

for i, file in enumerate(glob.glob('photos/*.jpg')):
    image = cv2.imread(file)
    image_gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    cv2.imwrite('./gray/grayscale_%03d.jpg' % i, image_gray)

Answer 2

You should check that whether you're on designed directory

# Check current working directory.
retval = os.getcwd()
print "Current working directory %s" % retval

Make sure that 'gray' filder is existed or not. I think there's no problem with your code.