Nelio lets you post a full landscape or portrait image to Instagram without needing to crop or cut it up.
The colours Nelio provides you with for your borders are taken directly from your photo to help them blend better with your image. Or, you can simply tap sections of your image to pull the specific colour that you desire directly from it.
Nelio also provides a smear tool that will smear the edge of your image to fill out the border, which can add a very unique and interesting effect to your final image.