Randomly generates an identicon. Parameters are width, height and a boolean for symmetry.

Identicon.sh

#!/usr/bin/env bash

bool='^[Tt][Rr][Uu][Ee]|[Ff][Aa][Ll][Ss][Ee]$'
digit='^[0-9]+$'
width=5
symmetrical=false

if [[ -n "$1" ]]; then
    if [[ "$1" =~ $digit ]]; then
        width=$(( $1 < 1 ? 1 : $1 ))
    elif [[ "$1" =~ $bool ]]; then
        symmetrical="${1,,}"
    fi
fi
if [[ -n "$2" ]]; then
    if [[ "$2" =~ $digit ]]; then
        height=$(( $2 < 1 ? 1 : $2 ))
    elif [[ "$2" =~ $bool ]]; then
        symmetrical="${2,,}"
    fi
fi
if [[ -n "$3" ]] && [[ "$3" =~ $bool ]]; then
    symmetrical="${3,,}"
fi

[[ -z "$height" ]] && height=$width

if $symmetrical; then
    (( width % 2 )) && remainder=true || remainder=false
    (( width /= 2 ))
fi

border=
if $symmetrical; then
    for (( w = 0; $w < $width; w++ )); do
        border+=$'\u2500\u2500\u2500\u2500'
    done
    $remainder && border+=$'\u2500\u2500'
else
    for (( w = 0; $w < $width; w++ )); do
        border+=$'\u2500\u2500'
    done
fi

printf '\u250C%b\u2510\n' "$border"
for (( s = $height; $s > 0; s-- )); do
    if $symmetrical; then
        line=
        reverse=

        for (( b = 0; $b < $width; b++ )); do
            line+=$(( $RANDOM & 1 ))
        done

        $remainder && line+=$(( $RANDOM & 1 ))

        for (( b = 0; $b < $width; b++ )); do
            reverse="${line:$b:1}$reverse"
        done

        line+="$reverse"
    else
        line=
        for (( b = 0; $b < $width; b++ )); do
            line+=$(( $RANDOM & 1 ))
        done
    fi

    line=${line//1/\\u2588\\u2588}
    line=${line//0/\\u0020\\u0020}
    printf '\u2502%b\u2502\n' "$line"
done
printf '\u2514%b\u2518\n' "$border"