Naive function that checks to see if a specific pixel is part of a green letterbox bar

check_for_green_bar.sh

RED_BOUNDARY="50" # less than
GREEN_BOUNDARY="250" # greater than
BLUE_BOUNDARY="20" # less than

# Usage: check_for_green_bar x-coord y-coord gravity
# Returns: 0 if pixel is bright green, 1 if pixel is not
function check_for_green_bar {
    color=$(convert thumbnail-gbc.jpg -crop "1x1+${1}+${2}" -gravity "${3}" txt:- | grep -oE 'srgb\(.+\)' | grep -oE '[0-9,]+')
    found_red=$(echo $color | grep -oE '^[0-9]+')
    found_green=$(echo $color | sed -E s/[0-9]+,// | grep -oE '^[0-9]+')
    found_blue=$(echo $color | sed -E s/[0-9]+,[0-9]+,// | grep -oE '^[0-9]+')
    if [[ ($found_red -le $RED_BOUNDARY ) && ($found_green -ge $GREEN_BOUNDARY) && ($found_blue -le $BLUE_BOUNDARY) ]];
    then
        echo 0
    else
        echo 1
    fi
}