#!/bin/bash

###########################
#
# Export a video to an image sequence at a 
# particular framerate.
#
###########################

MULTIPLE=3
FPS=24
RATE=`echo "scale=0;${FPS}/${MULTIPLE}" | bc`
TIMESTR=""

INPUT="${1}"
OUTPUT="${2}"
INVERT="${3}"
START_FRAME=${4}
END_FRAME=${5}

WIDTH=323 #80
HEIGHT=242 #60

if [[ "${INVERT}" != "" ]] && [[ "${INVERT}" == "negative" ]]; then
	INVERT="negate,"
else
	INVERT=""
fi

if [[ "${START_FRAME}" != "" ]]; then
	START=`echo "scale=6;${START_FRAME}/${FPS}" | bc`
	TIMESTR="${TIMESTR} -ss ${START}"
fi

if [[ "${END_FRAME}" != "" ]]; then
	TIME=`echo "scale=6;(${END_FRAME}-${START_FRAME})/${FPS}" | bc`
	TIMESTR="${TIMESTR} -t ${TIME}"
fi

mkdir -p "${OUTPUT}"

ffmpeg -y -re -r ${FPS} -i "${INPUT}" \
	${TIMESTR} \
	-f image2 \
	-r ${RATE} \
	-vf ${INVERT}crop=in_h/3*4:in_h,scale=$WIDTH:$HEIGHT,setsar=1:1 \
	-q:v 1 -qmin 1 -qmax 1 \
	"${OUTPUT}/image_%06d.png"