#!/bin/bash

#file numbers to start with
#Two variable must be given: background and foreground image folders.
#total number of original files are calculated by looking into the directories and picking the one with the most images

COUNT1=1
COUNT2=1

N1=`ls $1 | wc -l` 
N2=`ls $2 | wc -l`

highest_number=0
for x in $N1 $N2
do
if [ $x -gt $highest_number ]
then
highest_number=$x
fi
done

OTOTAL=$( echo "$highest_number / 4 " | bc )
# variables for degree of swirl and implosion as well as the name of the output file 

for i in $(seq 1 $OTOTAL); do

S_ARG=$(echo "$i * 15" | bc)
I_ARG=$(echo "scale=3; $i / 60" | bc)
VAR3=$(printf "%03d" $i)

# For the folder with less files in it.
# Reverts the number of the current file being called up to 001 when all files in the folder have been called.

if [ $COUNT1 -le $N1 ]; then
    VAR1=$(printf "%03d" $COUNT1)

else VAR1=$(printf "%03d" $COUNT1)
    COUNT1=1

fi 

if [ $COUNT2 -le $N2 ]; then
    VAR2=$(printf "%03d" $COUNT2)

else VAR2=$(printf "%03d" $COUNT2)
    COUNT2=1

fi

# Swirls and implodes a sequence of images. Composes it over a background sequence. 720x576 image sizes assumed
# shave and border necessary because otherwise there are vestiges of the whirlpool image at the sides.
convert $1/$VAR1.png \( $2/$VAR2.png -bordercolor none -border 150x150 -swirl $S_ARG -implode $I_ARG -shave 150x150 \) -compose src-over -composite $VAR3.png

echo " $VAR3 "
let COUNT1=COUNT1+4
let COUNT2=COUNT2+4

# Break once all files in the larger folder are called

if [ $VAR3 -eq $OTOTAL ]; then
break
fi

done