Find:

```
(\!\[\].*[/])(.*?)(\.png|],jpg|\.jpeg)(\))
```

Replace:

```
![$2](/assets/img/$2$3)
```

Results in
```
![](/assets/img/inserting+annotation+shows+on+graph.png)
changing to
![inserting+annotation+shows+on+graph](/assets/img/inserting+annotation+shows+on+graph.png)

```