如何重命名多个子文件夹中多个文件的扩展名（.jpg）？(How to rename the extension (.jpg) of multiple files in multiple subfolders?)

 我正在收集我所有的家庭相册，主要有几百个子文件夹，里面有数百张图片。 如何转换所有这些画廊而不在每个子文件夹中复制bat文件并在每个文件夹中运行它？ 
 
 我有超过1k的画廊，请帮忙！ 
 
 这是我试图写的命令： 
 
@ECHO OFF  FOR /f "delims=*" %a IN ('dir *.jpg /b /s') do REN "%a" *.png
 
 但是不行不通，我不知道我做错了什么.. 
 
 PS：文件夹和子文件夹仍然在通用位置，我没有固定的，因为我总是将文件从磁盘移动到其他人。 我正在使用Windows 8.1。 

I am collecting all my family albums in a main one with hundreds of subfolders that inside have hundreds of images. How I can convert all this galleries without to copy in each subfolder the bat file and run it in every folder?
 
I have more than 1k of galleries, please help!
 
This is the command what I tried to write:
 
@ECHO OFF  FOR /f "delims=*" %a IN ('dir *.jpg /b /s') do REN "%a" *.png
 
But insn't work and I don't know what I'm doing wrong.. 
 
PS: The folder and subfolders are still in generic location, I don't have a fixed one because I always move the files from a disk to others. I'm using Windows 8.1.

原文：https://stackoverflow.com/questions/35072793