gammad

A lightweight Linux utility for applying gamma correction to display outputs using DRM/KMS. This tool allows you to adjust the RGB color channels of your display, commonly used for blue light filtering or color temperature adjustments. This was made mainly to provide Night Light feature to Cosmic DE

Installation

Install Dependencies

sudo apt-get install libdrm-dev build-essential

Build

make

Install

sudo make install

Usage

gammad <card_name> <temperature>

Arguments

• card_name: Name of the DRM card (e.g., card0, card1)
• temperature: Color temperature in Kelvin (1000-10000)

Temperature

• 6500K = neutral white (daylight)
• 5000K = slightly warm
• 3000K = warm (evening)
• 2000K = very warm (night shift)

Example

gammad card1 3000

Finding Your Graphics Card

To list available DRM devices:

ls /dev/dri/

Cosmic DE

gammad should be injected right after shebang in /usr/bin/cosmic-greeter-start:

#!/bin/sh
gammad card1 3000
rm -rf /run/cosmic-greeter/cosmic/com.system76.CosmicSettingsDaemon/v1/* > /dev/null 2>&1
exec cosmic-comp cosmic-greeter > /dev/null 2>&1