debian - Software adjustment of LCD monitor brightness in Raspberry Pi

This is my first post here. I'm at the beginning of the road called Raspberry Pi.

Is there any way of changing the gamma/contrast/brightness of monitor via Raspberry Pi?

My Samsung 960BF doesn't have any hardware adjustment, only a power button.

I tried using xbacklight and got error

"No outputs have backlight property".

gddccontrol also didn't work. Error:

I/O warning: failed to load external entity "/home/pi/.dccontrol/monitorlist"  
   Document not parsed successfully
   Probing for available monitors"

And nothing is happening.

I connected my monitor through DVI-HDMI cable. Maybe this is why it doesn't work?

I'm using Raspberry Pi B+ V1.2 with Raspbian.