4

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.

0

One tool I have used successfully (not on a pi though), is xcalib from the package of the same name. You can use it to change the gamma, eg:

xcalib -gc 1.1 -a

You can repeat this. To cancel use

xcalib -clear

Another useful option is making the whole screen reverse-video:

 xcalib -invert -a

It is intended to work with icc profiles, but I have only used the above commands.

  • Thanks for reply. I tried this, but nothing happens, end after executing command: xcalib -b 99 there is an error: "Warning: Unable to read file ' ' " – tarzanno Jul 8 '15 at 13:44
  • You would need -b 99 -a but I wouldnt do that, the screen will be all white. – meuh Jul 11 '15 at 4:34
  • Unfortunately, it doesn't work either. I tried 'xcalib -b 99 -a', 'sudo xcalib -b 99 -a' , and 'xcalib -b 10 -a' to make sure my monitor is not set to max brightness already. There is no error and nothing is happening. I'm afraid that I will need to learn i2c and control the monitor by that... – tarzanno Jul 11 '15 at 11:47
  • Perhaps your cable is not passing through the i2c data line. Look in your /var/log/Xorg.0.log or similar log file to see if the display's eeprom was found (look for EDID). – meuh Jul 11 '15 at 12:12
  • Nothing like that exists in this file. There is only a line telling that Rpi is using default monitor and : "no device specified for default monitor section". Must I buy a new HDMI-DVI cable, or there is another way? – tarzanno Jul 11 '15 at 12:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.