#!/bin/bash -x
##########################
###### With the help of a gradient mask, sigmoidal-contrast effect and
###### Absolute Distortion LUT Map, an image sequence is gradually
###### squished and pulled down to the bottom of the screen. The image
###### sequence gradually arcs downwards at the sides by using arc
###### distort on the above mask. Finally, another gradient mask uses
###### arc distort to create a sunset-like fade-away to a background
###### image sequence. 
#########################
trap "rm -f *.list *.mpc *.cache" 1 2 3 15
trap "exit 0" 2

# Defaults needed only once for each sequence
Defaults () {
BOTTOM=`convert "$1" -format "%h" info:`	# heigth of the images !
WIDTH=`convert "$1" -format "%w" info:`		# width of the images !
MID=$(echo "$WIDTH / 2" | bc)			# mid-point of the width !
sig_con_end=50		# sigmoidal contrast with max effect !
sig_mid_end=100		# sigmoidal mid point with max effect !
arc_angle_end=150		# maximum radius of arc distortion !
 # start position of the bottom and top radius of arc distort in the fade
BOTTOM_RADIUS=$(echo " scale=2; sqrt ( ( $MID ^ 2 ) + ( $BOTTOM ^ 2 ) ) " | bc ) #X
TOP_RADIUS=$(echo " scale=2; $BOTTOM_RADIUS * 1.3 " | bc ) #X
SIG_CON_X=0			# start position for variable needed to calculate contrast of sigmoidal-contrast
SIG_MID_X=0			# start position for variable needed to calculate mid-point of sigmoidal-contrast
ARC_ANGLE=0				# start position of variable needed to calculate arc distort
arc_angle_start=1			# arc distort with no effect !
sig_con_start=1			# sigmoidal-contrast contrast with no effect !
sig_mid_start=50		# sigmoidal-contrast mid point with no effect !
# frame-to-frame change in position of the bottom and top radius of arc distort !
BOTTOM_RADIUS_CHANGE=$(echo " scale=2; $BOTTOM_RADIUS / $FADE_SUNSET" | bc) # !
TOP_RADIUS_CHANGE=$(echo " scale=2; ( $TOP_RADIUS - 1 ) / $FADE_SUNSET" | bc) # !
# frame-to-frame change in sigmoidal-contrast contrast and mid-point
SIG_CON_CHANGE=$(echo "scale=4; ( sqrt ( $sig_con_end - $sig_con_start ) ) / ( $SIG_ARC )  " | bc) # !
SIG_MID_CHANGE=$(echo "scale=4; ( sqrt ( $sig_mid_end - $sig_mid_start ) ) / ( $SIG_ARC )" | bc) # !
# frame-to-frame change in initial arc distort
ARC_ANGLE_CHANGE=$(echo "scale=4; ( sqrt ( $arc_angle_end - $arc_angle_start ) ) / ( $ARC_COUNT )" | bc) # !
# Writes various default variables to file so that they can exported from the parent process.
echo -e "export MID=$MID \n export WIDTH=$WIDTH \n export BOTTOM=$BOTTOM \n export sig_con_end=$sig_con_end \n export sig_con_start=$sig_con_start \n export sig_mid_end=$sig_mid_end \n export sig_mid_start=$sig_mid_start \n export arc_angle_end=$arc_angle_end \n export arc_angle_start=$arc_angle_start \n export TOP_RADIUS_CHANGE=$TOP_RADIUS_CHANGE \n export BOTTOM_RADIUS_CHANGE=$BOTTOM_RADIUS_CHANGE \n export SIG_CON_CHANGE=$SIG_CON_CHANGE \n export SIG_MID_CHANGE=$SIG_MID_CHANGE \n export ARC_ANGLE_CHANGE=$ARC_ANGLE_CHANGE">defaults-sunset.list
# Writes various variables to file for first image in sequence needing that variable
echo "ARC_ANGLE=$ARC_ANGLE">sigarc-vario.list
echo -e "TOP_RADIUS=$TOP_RADIUS \n BOTTOM_RADIUS=$BOTTOM_RADIUS">sunset-fade-vario.list
# Creates final LUT distortion mask before the fade !
convert -size "$WIDTH"x"$BOTTOM" gradient: -rotate 180 -sigmoidal-contrast "$sig_con_end","$sig_mid_end"% -distort arc "$arc_angle_end" +repage -gravity north -crop "$WIDTH"x"$BOTTOM"+0+0 -resize "$WIDTH"x"$BOTTOM"! +repage maskC.mpc # !
}

# Calculates sigmoidal-contrast distortion variables and writes them to file for the next image
SigVario () {
SIG_CON_X=$(echo " scale=4; $SIG_CON_CHANGE + $SIG_CON_X " | bc )
SIG_MID_X=$(echo " scale=4; $SIG_MID_CHANGE + $SIG_MID_X " | bc )
SIG_CON=$(echo " scale=4; ( $SIG_CON_X ^ 2 ) + $sig_con_start " | bc )
SIG_MID=$(echo " scale=4; ( $SIG_MID_X ^ 2 ) + $sig_mid_start " | bc )
echo -e "SIG_CON_X=$SIG_CON_X \n SIG_MID_X=$SIG_MID_X">sig-vario.list
}

# Same as above, but adds arc distort variables and fill-ins for the arc distort command
SigArcVario () {
. sig-vario.list
SigVario
ANGLE=$(echo " scale=4; ( $ARC_ANGLE ^ 2 ) + $arc_angle_start " | bc )
ARKFILL=" -distort arc "$ANGLE" +repage "
ARC_ANGLE=$(echo " scale=4; $ARC_ANGLE_CHANGE + $ARC_ANGLE " | bc )
MaskySigArc
echo "ARC_ANGLE=$ARC_ANGLE">sigarc-vario.list
}

# LUT distortion mask: gradient with variable sigmoidal-contrast and arc distort
MaskySigArc () {
MASK_LUT=" ( -size "$WIDTH"x"$BOTTOM" gradient: -rotate 180 -sigmoidal-contrast "$SIG_CON","$SIG_MID"% "$ARKFILL" -gravity north -crop "$WIDTH"x"$BOTTOM"+0+0 -resize "$WIDTH"x"$BOTTOM"! +gravity ) "
}

# LUT distortion mask: gradient with variable sigmoidal-contrast
MaskySig () {
MASK_LUT=" ( -size "$WIDTH"x"$BOTTOM" gradient: -rotate 180 -sigmoidal-contrast "$SIG_CON","$SIG_MID"% ) "
}

SunsetFadeVario () {
FILL_BACK=$1				# Adds background image to command
# New position of bottom and top radius of arc distort for next image
TOP_RADIUS=$(echo " scale=2; $TOP_RADIUS - $TOP_RADIUS_CHANGE " | bc )
BOTTOM_RADIUS=$(echo " scale=2; $BOTTOM_RADIUS - $BOTTOM_RADIUS_CHANGE " | bc )
SUNSET_FILL='( -filter point -size '$WIDTH'x'$BOTTOM' gradient: -set option:distort:viewport '$WIDTH'x'$BOTTOM'-'$MID'-'$BOTTOM' -distort arc 180,0,'$TOP_RADIUS','$BOTTOM_RADIUS' -negate ) -compose src-over -composite'
echo -e "TOP_RADIUS=$TOP_RADIUS \n BOTTOM_RADIUS=$BOTTOM_RADIUS">sunset-fade-vario.list
}

# Imagemagick command. Two gradients are combined - the second one
# having sigmoidal contrast and arc distort effects - and their RG
# channels act as a look-up map for the foreground image. Later
# another arc distorted gradient act as a mask to fade foreground to
# background image.
Sunset () {
convert $FILL_BACK \( $1 \( \( -size "$BOTTOM"x"$WIDTH" gradient: -rotate 90 \) $MASK_LUT -channel RGB  -combine \) -fx 'p{v.r*w,v.g*h}' \) $SUNSET_FILL $2
}

# Calls only one infile first...
Caller1 () {
INFILE1=`awk 'NR==1 {print $1}' caller.list`
OUTFILE=`awk 'NR==2' caller.list`
}
# and then calls the second one to act as the background
Caller2 () {
INFILE1=`awk 'NR==1 {print $1}' caller.list`
INFILE2=`awk 'NR==2 {print $1}' caller.list`
OUTFILE=`awk 'NR==3' caller.list`
}

if [ $COUNT = $DEFAULT_FETCH ]; then	# Creates defaults for this sequence
    Caller1
    Defaults $INFILE1
    SigVario
    MaskySig
    Sunset $INFILE1 $OUTFILE
elif [ $COUNT -le $COMPOSE1 ]; then	# Only sigmoidal-contrast performed on LUT
    . sig-vario.list
    Caller1
    SigVario
    MaskySig
    Sunset $INFILE1 $OUTFILE
elif [ $COUNT -le $COMPOSE2 ]; then	# Sigmoidal-contrast and arc-distort 
    . sigarc-vario.list
    SigArcVario
    Caller1
    Sunset $INFILE1 $OUTFILE
else					# Fade using mask
    . sunset-fade-vario.list
    Caller2
    SunsetFadeVario $INFILE2
    Sunset $INFILE1 $OUTFILE
fi