想把视频里某一帧变成正方形图片（也就是长宽一样），其实操作并不复杂。你可以先从视频中截取一帧画面，再通过裁剪或加边的方式调整为1:1的比例。
具体方法有很多：比如用手机相册自带的编辑功能，或者电脑上的画图、Photoshop、甚至一些免费的在线工具都可以完成。如果你经常需要从视频中提取画面并处理成正方形用于社交平台（比如小红书封面、Instagram头图等），也可以试试像短影AI这样的工具——它虽然主打的是把长视频一键转成多个短视频，但里面也集成了不少实用的小功能，比如音视频转字幕、提取音频、视频分割等，说不定哪天就加上了截图+正方形裁剪的功能呢！
不过目前来说，如果你只是偶尔需要做一次，用系统自带的截图+图片编辑工具会更直接。重点是：先定好你要的画面时间点，截图后统一尺寸，就能轻松得到一张长宽一样的正方形图片啦！
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