#/usr/bin/bash

output=$(v4l2-ctl --device=/dev/video4 --list-ctrls)
brightness=$(echo "$output" | grep "brightness" | grep -oP 'value=\K\d+')
contrast=$(echo "$output" | grep "contrast" | grep -oP 'value=\K\d+')

CMD="v4l2-ctl --device=/dev/video4 --set-ctrl="

case $1 in
  b)  # Brightness
    if [ "$2" = 'u' ]; then
      bash -c "${CMD}brightness=$((brightness + 2))"
    elif [ "$2" = 'd' ]; then
      bash -c "${CMD}brightness=$((brightness - 2))"
    fi
    ;;
  c)  # Contrast
    if [ "$2" = 'u' ]; then
      bash -c "${CMD}contrast=$((contrast + 2))"
    elif [ "$2" = 'd' ]; then
      bash -c "${CMD}contrast=$((contrast - 2))"
    fi
    ;;
  *)
    echo "Usage: $0 [b|c] [u|d]"
    ;;
esac