There are two images: *a.jpg* and *b.jpg*.

I just want to know how to join them into one image using `ffmpeg`.

How should I finish the `ffmpeg -i a.jpg -i b.jpg` command to get a *c.jpg* output image?

This is an example of what I am trying to achieve:

1. *a.jpg*

![a.jpg](https://i.stack.imgur.com/qgOYV.jpg)
2. *b.jpg*

![b.jpg](https://i.stack.imgur.com/8K4VM.jpg)
3. *c.jpg*

![a.jpg and b.jpg side-by-side on one image](https://i.stack.imgur.com/WCrOL.png)