#!/bin/bash


ANGLE=0 # angle of the pictures in the first file
COUNT=1 # number to start with to call the original files (usually not changed)
ETOTAL=400 # total number of end files
YVALUE=-1 # angle of the pictures in the first file
FLIP=201 # number of images it takes to complete one flip
OTOTAL=250 # Total number of original files
COUNT2=1 # number to start naming the files with

# calls up the names of the original files
while [ $COUNT -le $OTOTAL ]; do
if [ $COUNT -lt $OTOTAL ]; then
    VAR=`printf "%03d" $COUNT`
elif [ $COUNT -eq $OTOTAL ]; then
    COUNT=0
    VAR=$OTOTAL
fi

# repage to put the center of the rotation in the middle of the original picture. use $angle to calculate affine rotation.
# crop creates pal background. Changing the $yvalue makes the animation flip head over heals 
convert $VAR.jpg -affine `affine_distort 180,144 1,$YVALUE $ANGLE 360,288` -transform -crop 720x576+0+0\! -background white -flatten test/$VAR2.jpg

echo $VAR
let COUNT=COUNT+1

# calculates the current angle of the animation so that it spins 360 degrees
ANGLE=$(echo "scale=2; $ANGLE + 360 / $ETOTAL" | bc)


# counts from -1 to 1 and back. changes the yvalue of the images to create the flip effect. 
# the value in the parenthesis comes from the difference from -1 to 1 and half of the number of files
# because the sequence is fliped back to the original position
if [ $COUNT2 -lt $FLIP ]; then
YVALUE=$(echo "scale=2; $YVALUE + ( 2 / ( $ETOTAL / 2 )" | bc)

elif [ $COUNT2 -ge $FLIP ]; then
YVALUE=$(echo "scale=2; $YVALUE - ( 2 / ( $ETOTAL / 2 )" | bc)
fi

# gives the file names
if [ $COUNT2 -le $ETOTAL ]; then
    VAR2=`printf "%04d" $COUNT2`
elif [ $COUNT2 -gt $ETOTAL ]; then
break
fi

let COUNT2=COUNT2+1
done