A bash script using streamer and convert to detect the ambient room brightness using webcam.

roomdark.sh

#!/bin/bash

filename=capture.ppm

streamer -o $filename >/dev/null 2>&1

rgb=$(convert $filename -resize 1x1 txt:- | sed -n 2p | grep -Po "#\w+" | cut -c 2-)

if [[ 0x$rgb -lt 0x212121 ]]
then
	echo yes
else
	echo no
fi

rm $filename