Get full timestamp (HH:MM:SS) from input (MM:SS, H:MM:SS, H:M:S, etc.)

gistfile1.txt

#!/bin/bash
cat $1 |
while read cnt tm; do
    cnt=$((cnt-1))
    IFS='.' read -a a <<< "$tm"
    MVAR=0
    SVAR=1
    HOUR=00
    # check if string has hours included (ex: 01:23:45)
    if [ -n "${a[2]}" ]; then
        if [ ${#a[0]} -lt 2 ]; then
            HOUR="0"${a[0]}
            MVAR=1
            SVAR=2
        else
            HOUR=${a[0]}
        fi
    fi

    # let's keep processing our minutes and seconds
    if [ ${#a[$MVAR]} -eq 1 ]; then
        MINUTE="0"${a[$MVAR]}
    else
        MINUTE=${a[$MVAR]}
    fi
    if [ ${#a[$SVAR]} -lt 2 ]; then
        SECOND="0"${a[$SVAR]}
    else
        SECOND=${a[$SVAR]}
    fi
    TIME=$HOUR:$MINUTE:$SECOND
    echo "{\"kind\":\"image\",\"time\":\"$TIME\",\"filename\":\"slide"$cnt".png\",\"title\":\"\"},"
done