bboxmerge

#!/usr/bin/env bash
PROGRAM_NAME=$(basename "$0")

function usage {
    echo "Merge (union) multiple bounding boxes into a single bounding box"
    echo ""
    echo "usage: $PROGRAM_NAME <bbox>"
    echo "    - <bbox|-(bbox objects on stdin>: \$minx,\$miny,\$maxx,\$maxy"
    exit 1
}

if test "$#" -lt 1; then
    usage
fi

set -euo pipefail

# shellcheck disable=SC2124
BBOXS="${@:1}"

function get_min(){
    local i="$1"   # Save first argument in a variable
    shift            # Shift all arguments to the left (original $1 gets lost)
    local vector=("$@") # Rebuild the array with rest of arguments
    min=$(echo "${vector[0]}" | awk -F, "{print \$$i}")
    for bbox in "${vector[@]}"; do
        val=$(echo "$bbox" | awk -F, "{print \$$i}")
        (( $(echo "$val < $min" | bc -l) )) && min=$val
    done
    echo "$min"
}

function get_max(){
    local i="$1"   # Save first argument in a variable
    shift            # Shift all arguments to the left (original $1 gets lost)
    local vector=("$@") # Rebuild the array with rest of arguments
    max=$(echo "${vector[0]}" | awk -F, "{print \$$i}")
    for bbox in "${vector[@]}"; do
        val=$(echo "$bbox" | awk -F, "{print \$$i}")
        (( $(echo "$val > $max" | bc -l) )) && max=$val
    done
    echo "$max"
}

if [[ $BBOXS == "-" ]];then
# BBOX passed on stdin
    if [ -t 0 ]; then
    # if do not allow interactive tty
        usage
    fi
    BBOXS=$(</dev/stdin)
    BBOXS=$(echo "$BBOXS" | tr '\r\n' ' ')
fi

IFS=' ' read -r -a BBOXS_ARRAY <<< "$BBOXS"
min_x=$(get_min "1" "${BBOXS_ARRAY[@]}")
min_y=$(get_max "2" "${BBOXS_ARRAY[@]}")
max_x=$(get_max "3" "${BBOXS_ARRAY[@]}")
max_y=$(get_max "4" "${BBOXS_ARRAY[@]}")
echo "${min_x},${min_y},${max_x},${max_y}"