#!/bin/bash -x
######################
#### "tractor-beam" is a compositing effect using imagemagick on a
#### sequence of images. Uses the imagemagick option distort
#### perspective on an image and then composites it over another. Also
#### makes use of masks to create a wipe at the end.
######################
trap "rm -f folder-list caller *.mpc *.cache" 1 2 3 15
trap "exit 0" 2
# These are variables for "tractor-beam" which only have to be set
# once every time "tractor-beam" is used.
Defaults () {
NEWBOTTOM=$BOTTOM				# remembers original image height #X=this
NEWMID=$(echo " scale=1; $MID - 0.5 " | bc )	# subtracts half-pixel from width: imagemagick half-pixel problem !
PERSP_CHANGE=$(echo "scale=3; ( ( $BOTTOM - 4 ) / 2 ) / $TRACTOR" | bc) # perspective distortion speed !
TOP=0						# remembers top end of image
GRAY=$(echo " $MID * 0.1" | bc)		# grayscale width for wipe !
WHITE=1						# Starting value for whiteout
WHITE_SPEED=$(echo " scale=2; 3 / $FADE_TRACTOR" | bc)	# white-out speed !
WIPE=0						# Starting value to chop the mask; creates wipe
WIPE_SPEED=$(echo " scale=2; (( $WIDTH + $GRAY - ( $GRAY / 10 )) / 2 ) / $FADE_TRACTOR " | bc) # speed of wipe !
BARRELA=0					# start position of barrel distort
BARRELD=1					# start position of barrel distort
BARREL_CHANGE=$(echo " scale=3; 1 / $COMPOSE " | bc) # Amount the barrel distort should be changed per frame
ENDBARRELA=$(echo "scale=3; $BARREL_CHANGE * $TRACTOR" | bc) # Not sure why this is here
ENDBARRELD=$(echo "scale=3; 1 - ( $BARREL_CHANGE * $TRACTOR )" | bc) # Not sure why this is here
ENDTOP=$(echo "scale=3; $PERSP_CHANGE * $TRACTOR" | bc) # Not sure why this is here
ENDBOTTOM=$(echo "scale=3; $BOTTOM - $ENDTOP " | bc) # Not sure why this is here
# Defaults are saved in a file, so that they can be exported as
# variable in the parent process "master"
echo -e "export NEWMID=$NEWMID \n export PERSP_CHANGE=$PERSP_CHANGE \n export WHITE_SPEED=$WHITE_SPEED \n export WIPE_SPEED=$WIPE_SPEED \n export BARREL_CHANGE=$BARREL_CHANGE ">defaults-tractor.list
# Masks needed for the wipe at the end of the effect: A gradient and a
# cookie cutter that gives the gradient the same shape as the image
# who's perspective has been distorted. !
convert -size "$MID"x"$BOTTOM" xc:white \
    \( -size "$BOTTOM"x"$GRAY" gradient:transparent-white -rotate 90 \) \
+append maskA.mpc
# Writes various variables to file for first image in sequence needing that variable
echo -e "WIPE=$WIPE\nWHITE=$WHITE \n TOP=$ENDTOP \n NEWBOTTOM=$ENDBOTTOM \n BARRELA=$ENDBARRELA \n BARRELD=$ENDBARRELD">vario-fade.list
}

# Change to the top and bottom of the right and left sides to create a
# squeeze effect on the sides. Barrel distort curves the lines. The
# file vario.list remembers the variables for when the process is
# recalled for the next file.
VarioPerspective () {
TOP=$(echo "scale=2; $TOP + $PERSP_CHANGE " | bc)
NEWBOTTOM=$(echo "scale=3; $NEWBOTTOM - $PERSP_CHANGE " | bc)
BARRELA=$(echo " scale=3; $BARRELA + $BARREL_CHANGE " | bc )
BARRELD=$(echo " scale=3; $BARRELD - $BARREL_CHANGE " | bc )
echo -e "TOP=$TOP \n NEWBOTTOM=$NEWBOTTOM \n BARRELA=$BARRELA \n BARRELD=$BARRELD ">vario.list
}

# Set whiteout and wipe effects at the end of the composition. WIPE
# and WHITE variables change file to file to create the
# whiteout-wipe. The file vario-fade.list remembers the variables for
# when the process is called for the next file.
VarioFade () {
LEFT_GRADIENT='-fx 'u*$WHITE' ( maskA.mpc -chop '$WIPE'x0 ) -compose dstin -composite'
RIGHT_GRADIENT='-fx 'u*$WHITE' ( maskA.mpc -flop -gravity east -chop '$WIPE'x0 ) -compose dstin -composite'
WIPE=$(echo "scale=3; $WIPE + $WIPE_SPEED" | bc)
WHITE=$(echo "scale=3; $WHITE + $WHITE_SPEED" | bc)
BARRELA=$(echo " scale=3; $BARRELA + $BARREL_CHANGE " | bc )
BARRELD=$(echo " scale=3; $BARRELD - $BARREL_CHANGE " | bc )
echo -e "WIPE=$WIPE\nWHITE=$WHITE\n BARRELA=$BARRELA \n BARRELD=$BARRELD \n TOP=$TOP \n NEWBOTTOM=$NEWBOTTOM">vario-fade.list
}

# Composition effect: squeezes together the top and bottom sides of
# the right and left sides and then does a barndoor wipe which whites
# out towards the sides
Magick () {
convert $2 \( $1 -crop 50%x100%+0+0 -alpha on -virtual-pixel transparent -distort perspective ' 0,0 0,'$TOP' 0,'$BOTTOM' 0,'$NEWBOTTOM' '$NEWMID','$BOTTOM' '$MID','$BOTTOM' '$NEWMID',0 '$MID',0 ' $LEFT_GRADIENT \( $1 -gravity east -crop 50%x100%+0+0 -alpha on -virtual-pixel transparent -distort perspective '0.5,0 0,0 0.5,'$BOTTOM' 0,'$BOTTOM' '$MID','$BOTTOM' '$MID','$NEWBOTTOM' '$MID',0 '$MID','$TOP'' $RIGHT_GRADIENT  \) +append -distort barrel '0.0 0.0 0.0 1.0 '$BARRELA' 0.0 0.0 '$BARRELD'' \) -compose src-over -composite $3
}

# Calls up infile and outfile names from caller.list file created by call-files script
Caller () {
INFILE1=`awk 'NR==1 {print $1}' caller.list`
INFILE2=`awk 'NR==2 {print $1}' caller.list`
OUTFILE=`awk 'NR==3' caller.list`
}

# Order of the composition. First runthrough makes sure default values
# are saved, second does perspective change along with barrel distort,
# third creates final mask for the fourth - the wipe-whiteout.
if [ $COUNT = $DEFAULT_FETCH ]; then
    Caller				
    Defaults
    Magick $INFILE1 $INFILE2 $OUTFILE
    VarioPerspective
elif [ $COUNT -le $COMPOSE1 ]; then
    . vario.list
    Caller
    Magick $INFILE1 $INFILE2 $OUTFILE
    VarioPerspective
else
    . vario-fade.list
    Caller
    VarioFade
    Magick $INFILE1 $INFILE2 $OUTFILE
fi