Image/color is brigtened when flipping

Hi, I [fork](https://github.com/fikr4n/android-flip) your project so it can be compiled with new compilation tools (Android Studio). Not sure why, but I got it become brighten when flipping.

![Screenshot](https://user-images.githubusercontent.com/5564999/48237005-5e1a2880-e3f7-11e8-906e-fcb87aab3283.png)
