如何区分空映像和有效映像？

Question

我测试一个代码，它的一个输出是一个图像。 我需要确保图像有一个有效的输出，但如果它是空的，我似乎无法从检查部分的有效图像中分辨出来

我能看出的唯一区别是一个名为src的字段，其中空图像可能如下所示：

<img src=data:image/png;base64,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 width="572" height="400">

而对于有效图像，src字段要长得多。 有没有一个python命令可以通过链接分析图像，看看它是否太。。。“白色”

另外，我注意到在我刚才引用的字段中有一个重复的子字符串“pAZBhWgBkmBYAGaYFQIZ”。这有意义吗

Answer 1

如果您只想检查图像当前是否存在于特定的URL中，那么有一种非常简单的方法来检查它

from urllib.request import urlopen
import requests
image_formats = ("image/png", "image/jpeg", "image/gif")
url = "http://localhost/img.png"
site = urlopen(url)
meta = site.info()  # get header of the http request
if meta["content-type"] in image_formats:  
    print("it is an image")

更多此类解决方案/备选方案可在check if a URL to an image is up and exists in Python中找到