Yup, the Tapatalk app. When you click on a reply, you will have a view like this.
Click on the plus sign next to the message box and it will change the view to look like this
If you press on the icon just to the right of the camera icon, it will automatically take you to the pictures stored in your phone. Click on the pic you want and it will automatically upload it. A Nice feature is it makes it easy to place a photo right where you want it in a post