This is a very simple app. It only has one function: the paintbrush. If you think that having just one function means that this program is too simple, you're very wrong. You can apply so many effects using Pixo that it will seem like it's a tool with infinite options.
Its interface is very comfortable. You won't find the mess of undecipherable tools that you usually find in other apps. Pixo has a section at the right where you will find all of the effects that you can apply, and you can regulate the intensity of these tools using the bar at the bottom.
You will have to use the paintbrush to select which areas of the image you want to apply the effect to, and then select its size in order to carry out your editing very precisely.
15 day trial version.