#!/usr/bin/env bash

# run this in the directory containing pngs


image_array=(*.png)

strStart="ffmpeg"
strInput=""
strFilter=""
strEnd="concat=n=${#image_array[@]}:v=1:a=0,format=yuv420p[v]\" -map \"[v]\" out.mp4"


# build input string
for i in ${image_array[@]}; do
    strInput="$strInput -loop 1 -t 5 -i $i"
done


strInput="$strInput -filter_complex"

# build filter string
for (( x=0; x<${#image_array[@]}; x++ )); do
    if [[ $x == 0 ]];then
        strFilter="\"[0:v]fade=t=out:st=4:d=1[v0];"
    else
        strFilter="$strFilter ["$x":v]fade=t=in:st=0:d=1,fade=t=out:st=4:d=1[v"$x"];"
    fi
    strNumber="$strNumber[v"$x"]"
done

# view the command
echo "Running ==> $strStart $strInput $strFilter $strNumber $strEnd"
echo
echo

# run built command
bash -c "$strStart $strInput $strFilter $strNumber $strEnd"