Help me calibrate iPhone display (jailbroken)

The gamma across the board (grays/red/green/blue/cyan/magenta/yellow) are at 1.0 on my 5s which is pretty bad, though I may not be checking with the most appropriate method. I think it's supposed to be somewhere around 2.2, and I need help figuring out what app/tweak will let me do that.

The device is jailbroken so I was able to download and use Color Profiles by Ryan Petrich, but I can't seem to get it to adjust the gamma. Does anyone know what App/tweak will let me do this?

I've been using pictures on the iPhone like the following one, for each color (gray/red/green/blue/cyan/magenta/yellow). They were taken as screenshots form a display calibration app for the Nexus 5, so they may not even be appropriate, but something's definitely off on my phone and I'd like to know what I need to do to adjust the gamma levels.