如何使用python的请求通过opencv从URL打开图像

Question

I am trying to open a large list of images using OpenCV on python, because I need to work with them latter.

Actually, I can achieve this goal with pillow like this:

url = r'https://i.imgur.com/DrjBucJ.png'
response = requests.get(url, stream=True).raw
guess = Image.open(response).resize(size)

I am using the library requests from python.

The response looks like this: b'\\x89PNG\\r\\n\\x1a\\n\\x00\\x00\\x00\\rIHDR\\x00\\x00\\x01\\xdb\\...

And if I am not wrong, those are the values of the pixels from the image of the url, correct?

My question is: how can I do the same with OpenCV?

I have tried it like:

resp = requests.get(url)
image = np.asarray(bytearray(resp.read()), dtype="uint8")
image = cv2.imdecode(image, cv2.IMREAD_COLOR)

And I get this error:

image = np.asarray(bytearray(resp.read()), dtype="uint8")
AttributeError: 'Response' object has no attribute 'read'

I got the code from this web: https://www.pyimagesearch.com/2015/03/02/convert-url-to-image-with-python-and-opencv/

Answer 1

You just forgot stream=True and .raw in requests.get

resp = requests.get(url, stream=True ) .raw

import cv2
import numpy as np
import requests

url = r'https://i.imgur.com/DrjBucJ.png'
resp = requests.get(url, stream=True).raw
image = np.asarray(bytearray(resp.read()), dtype="uint8")
image = cv2.imdecode(image, cv2.IMREAD_COLOR)

# for testing
cv2.imshow('image',image)
cv2.waitKey(0)
cv2.destroyAllWindows()

---

To answer your question

.raw mean that you want to retrieve the response as a stream of bytes and the response will not evaluated or transformed by any measure (so it will not decode gzip and deflate transfer-encodings) but with .content The gzip and deflate transfer-encodings are automatically decoded for you .

In your case it will be better to use .content over .raw

the following note from Requests package documentation

Note An important note about using Response.iter_content versus Response.raw. Response.iter_content will automatically decode the gzip and deflate transfer-encodings. Response.raw is a raw stream of bytes – it does not transform the response content. If you really need access to the bytes as they were returned, use Response.raw.

References:

https://2.python-requests.org/en/master/user/quickstart/#raw-response-content

https://2.python-requests.org/en/master/user/quickstart/#binary-response-content

Answer 2

@ Mohamed Saeed 's answer solved your problem. Below is an alternative solution to fetch image from a url:

import cv2
import numpy as np
from urllib.request import urlopen

req = urlopen('https://i.imgur.com/DrjBucJ.png')
image = np.asarray(bytearray(req.read()), dtype=np.uint8)
image = cv2.imdecode(image, -1) 

cv2.imshow('image',image)
cv2.waitKey(0)
cv2.destroyAllWindows()