为什么各种JPEG扩展？ [英] Why the various JPEG Extensions?

问题描述

在处理下载程序时，我遇到了以下Python的 mimetypes.guess_extension 函数：

While working on a downloader, I've encountered the following with Python's mimetypes.guess_extension function:

In [2]: mimetypes.guess_extension('image/jpeg', strict=False)
Out[2]: '.jpe'

我知道 jpeg 和 jpg 是有效的JPEG扩展，但我没有了解 jpe 。所以查看维基百科网站确实揭示了以下内容：

I knew that jpeg and jpg are valid JPEG extensions, but I didn't know about jpe. So looking at the wikipedia site did reveal the following:

使用JPEG压缩的文件最常见的文件扩展名是.jpg和.jpeg，虽然也使用.jpe，.jfif和.jif

The most common filename extensions for files employing JPEG compression are .jpg and .jpeg, though .jpe, .jfif and .jif are also used

我还不知道更多扩展名。

Even more extensions I didn't know of.

所以主要问题：为什么JPEG有这么多（有效）扩展名与它相关联？

So the main question: Why does JPEG have so many (valid) extensions associated with it?

在相关的说明中我'我想知道为什么Python确实返回'jpe'而不是'jpg'或'jpeg'，因为我看到这些使用最多。

On a related note I'd like to know why Python does return 'jpe' and not 'jpg' or 'jpeg' since I see these used the most.

推荐答案

出现 mimetypes.guess_extension 返回所有可能的扩展中的第一个：

It appears mimetypes.guess_extension returns the first of all possible extensions:

def guess_extension(self, type, strict=True):
    # ...
    extensions = self.guess_all_extensions(type, strict)
    if not extensions:
        return None
    return extensions[0]

所以你会得到以 mimetypes.guess_all_extensions 返回的列表中的第一个，结果是：

So you'll get whichever is first in the list returned by mimetypes.guess_all_extensions, which turns out to be:

>>> mimetypes.guess_all_extensions('image/jpeg', strict=False)
['.jpe', '.jpg', '.jpeg']

我猜为什么 .jpe 也有效：

在DOS和早期Windows版本中，文件名只能包含8个字符和3个字符（参见文章维基百科上的8.3文件名以获取更多信息）。可能是他们将JPEG缩写为.JPE或.jpe - 这就是为什么我们现在有.j​​pe，.jpeg和.jpg。

In DOS and early Windows versions filenames could only have 8 characters and 3 characters for the extension (see the article 8.3 filename on Wikipedia for more info). It could be that they abbreviated JPEG to .JPE or .jpe - which is why we now have .jpe, .jpeg and .jpg.

确实如此.jpeg和.jpg更常见。

It's indeed true that .jpeg and .jpg are more common.

这篇关于为什么各种JPEG扩展？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！