python-3.x - 如何使用 Python 3 从 S3 获得的 OpenCV 读取图像？

Question

我的 S3 存储桶文件夹中有一堆图像。

我有来自 S3 ( img_list ) 的 key 列表，我可以读取和显示图像:

key = img_list[0]
bucket = s3_resource.Bucket(bucket_name)
img = bucket.Object(key).get().get('Body').read()

我有一个功能:

def image_from_s3(bucket, key):

    bucket = s3_resource.Bucket(bucket)
    image = bucket.Object(key)
    img_data = image.get().get('Body').read()

    return Image.open(io.BytesIO(img_data))

现在我想要的是使用 OpenCV 读取图像，但出现错误:

key = img_list[0]
bucket = s3_resource.Bucket(bucket_name)
img = bucket.Object(key).get().get('Body').read()
cv2.imread(img)


SystemError                               Traceback (most recent call last)
<ipython-input-13-9561b5237a85> in <module>
      2 bucket = s3_resource.Bucket(bucket_name)
      3 img = bucket.Object(key).get().get('Body').read()
----> 4 cv2.imread(img)

SystemError: <built-in function imread> returned NULL without setting an error

请建议如何以正确的方式阅读它？

Answer 1

对不起，我在评论中弄错了。此代码在内存缓冲区中设置一个 PNG 文件来模拟您从 S3 获得的内容:

#!/usr/bin/env python3

from PIL import Image, ImageDraw
import cv2

# Create new solid red image and save to disk as PNG
im = Image.new('RGB', (640, 480), (255, 0, 0))
im.save('image.png')

# Slurp entire contents, raw and uninterpreted, from disk to memory
with open('image.png', 'rb') as f:
   raw = f.read()

# "raw" should now be very similar to what you get from your S3 bucket

现在，我只需要这个:

nparray = cv2.imdecode(np.asarray(bytearray(raw)), cv2.IMREAD_COLOR)

所以，你应该需要:

bucket = s3_resource.Bucket(bucket_name)
img = bucket.Object(key).get().get('Body').read()
nparray = cv2.imdecode(np.asarray(bytearray(img)), cv2.IMREAD_COLOR)