#!/bin/bash -x
######################
#### Same as "tractor-beam" composition except everything is performed backwards.
######################
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 () {
BOTTOM=`convert "$1" -format "%h" info:`	# heigth of the images !!
WIDTH=`convert "$1" -format "%w" info:`		# width of the images !!
MID=$(echo "$WIDTH / 2" | bc)			# mid-point of the width !!
NEWMID=$(echo " scale=1; $MID - 0.5 " | bc )	# subtracts half-pixel from width: imagemagick half-pixel problem !!
PERSP_CHANGE=$(echo "scale=3; ( ( $BOTTOM - 4 ) / 2 ) / $TRACTOR" | bc) # perspective distortion speed !!
TOP=$(echo "scale=3; $PERSP_CHANGE * $TRACTOR" | bc) #Start position for outer top edge of beam
NEWBOTTOM=$(echo "scale=3; $BOTTOM - $TOP " | bc) #Start position for outer bottom edge of beam
GRAY=$(echo " $MID * 0.1" | bc)		# grayscale width for wipe !!
WHITE_SPEED=$(echo " scale=2; 3 / $FADE_TRACTOR" | bc)	# white-out speed !!
WHITE=$(echo " scale=2; 1 + ( $WHITE_SPEED * $FADE_TRACTOR )" | bc) #start brightness of white-in fade
WIPE_SPEED=$(echo " scale=2; (( $WIDTH + $GRAY - ( $GRAY / 10 )) / 2 ) / $FADE_TRACTOR " | bc) # speed of wipe !!
WIPE=$(echo " scale=2; $WIPE_SPEED * $FADE_TRACTOR " | bc) #start position of wipe-in
BARREL_CHANGE=$(echo " scale=3; 1 / $COMPOSE " | bc) # speed of barrel distortion change
BARRELA=$(echo " scale=3; $BARREL_CHANGE * $COMPOSE " | bc) # start value for barrel distortiong
BARRELD=$(echo " scale=3; 1 - ( $BARREL_CHANGE * $COMPOSE ) " | bc) #start value for barrel distortion
ENDBARRELA=$(echo " scale=3; $BARREL_CHANGE * $TRACTOR    " | bc) # not sure what this is for
ENDBARRELD=$(echo " scale=3; 1 - ( $BARREL_CHANGE * $TRACTOR )" | bc) #not sure what this is for
# Defaults are saved in a file, so that they can be exported as
# variable in the parent process "master"
echo -e "export WIDTH=$WIDTH \n export BOTTOM=$BOTTOM \n export MID=$MID \n 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=$BARREL_CHANGE \n export TOP=$TOP \n export NEWBOTTOM=$NEWBOTTOM ">defaults-tractor.list
# Masks needed for the wipe at the end of the effect: A gradient and a
# cookie cutter that gives the gradient the same shape as the image
# who's perspective has been distorted. !!
convert -size "$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 "BARRELA=$ENDBARRELA \n BARRELD=$ENDBARRELD ">vario.list
}

# Change to the top and bottom of the right and left sides to create a
# squeeze effect on the sides, barrel distort gives edges a curve. 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 () {
WIPE=$(echo "scale=2; $WIPE - $WIPE_SPEED" | bc)
WHITE=$(echo "scale=2; $WHITE - $WHITE_SPEED" | bc)
BARRELA=$(echo " scale=3; $BARRELA - $BARREL_CHANGE " | bc )
BARRELD=$(echo " scale=3; $BARRELD + $BARREL_CHANGE " | bc )
LEFT_GRADIENT='-fx 'u*$WHITE' ( maskA.mpc -chop '$WIPE'x0 ) -compose dstin -composite'
RIGHT_GRADIENT='-fx 'u*$WHITE' ( maskA.mpc -flop -gravity east -chop '$WIPE'x0 ) -compose dstin -composite'
echo -e "WIPE=$WIPE\nWHITE=$WHITE\n BARRELA=$BARRELA \n BARRELD=$BARRELD">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 () {
INFILE2=`awk 'NR==1 {print $1}' caller.list`
INFILE1=`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 wipe-in white in, third does perspective
# un-distort of side along with barrel distort.
if [ $COUNT = $DEFAULT_FETCH ]; then
    Caller				
    Defaults $INFILE1
    VarioFade
    Magick $INFILE1 $INFILE2 $OUTFILE
elif [ $COUNT -le $COMPOSE1 ]; then
    . vario-fade.list
    VarioFade
    Caller
    Magick $INFILE1 $INFILE2 $OUTFILE
else
    . vario.list
    VarioPerspective
    Caller
    Magick $INFILE1 $INFILE2 $OUTFILE
fi