Add shell code

Readme.md

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+# brightness
+
+Set the screen brightness using your camera.

brightness.sh

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+#!/bin/env bash
+
+# camera device
+FFMPEG_DEVICE='/dev/video0'
+# min brightness
+MIN=50
+# get max brightness
+MAX=$(cat /sys/class/backlight/intel_backlight/max_brightness)
+# sys path for backligt control
+SET='/sys/class/backlight/intel_backlight/brightness'
+
+# get grayscale and calculate brightness value for the screen
+GET_GRAYSCALE=$(ffmpeg -i $FFMPEG_DEVICE -vf scale=1:1 -pix_fmt gray -f rawvideo -frames:v 1 -v quiet pipe:1)
+AMBIENT=$(echo -n $GET_GRAYSCALE | od -t u | sed "s/000000[01]\s*//" | sed q)
+BRIGHTNESS=$(( $AMBIENT * $MAX / 255 ))
+
+# set brightness and limit boundaries
+echo $(( $BRIGHTNESS > $MIN ? $BRIGHTNESS : $MIN )) | sudo tee $SET