#!/bin/bash

 #

 # requires: ...topnm, pnmscale, pnmcomp, ppmntsc, ppmtoy4m, mpeg2enc

 #

 # video format. pal or ntsc

 FORMAT=pal

 # target image width/height (taking into account visible screen area)

 if [ "$FORMAT" = "ntsc" ]; then

   TW=600

   TH=420

 else

   TW=632

   TH=512

 fi

 TMP=/tmp/image_convert.$$.pnm

 IMG=$1

 MPG=$2

 DIR=`dirname "$MPG"`

 if [ ! -d "$DIR" ]; then

   mkdir -p "$DIR"

 fi

 #

 # get the file type and set the according converter to PNM

 #

 FILE_TYPE=`file -i -L -b "$IMG" 2>/dev/null | cut -f2 -d/`

 case "$FILE_TYPE" in

   jpg | jpeg)

   TO_PNM=jpegtopnm

   ;;

   tiff)

   TO_PNM=tifftopnm

   ;;

   bmp | x-bmp)

   TO_PNM=bmptoppm

   ;;

   png | x-png)

   TO_PNM=pngtopnm

   ;;

   Netpbm | pnm | x-portable-pixmap)

   TO_PNM=cat

   ;;

   gif)

   TO_PNM=giftopnm

   ;;

   *)

   echo "filetype '$FILE_TYPE' is not supported"

   exit 1

   ;;

 esac

 #

 # 'chroma subsampling mode' mjpegtools >= 1.8.0

 #

 SUBSAMPLINGMODE=""

 if ppmtoy4m -h 2>&1 | egrep -q "'420mpeg2'"; then

     SUBSAMPLINGMODE="-S 420mpeg2"

 fi

 #

 # extract the image size & compute scale value

 #

 LANG=C # get the decimal point right

 $TO_PNM "$IMG" >$TMP 2>/dev/null

 S=`pnmfile $TMP | awk '{ printf "%d %d ",$4,$6 }'`

 S=`echo $S $TW $TH | awk '{ sw=$3/$1; sh=$4/$2; s=(sw<sh)?sw:sh; printf "%.4f\n",(s>1)?1.0:s; }'`

 #

 # now run the conversion

 #

 if [ "$FORMAT" = "ntsc" ]; then

   pnmscale $S $TMP | \

     pnmpad -black -width 704 -height 480 | \

     ppmntsc | \

     ppmtoy4m -v 0 -n 1 -r -F 30000:1001 $SUBSAMPLINGMODE | \

     mpeg2enc -f 7 -T 90 -F 4 -nn -a 2 -v 0 -o "$MPG"

 else

   pnmscale $S $TMP | \

     pnmpad -black -width 704 -height 576 | \

     ppmntsc --pal | \

     ppmtoy4m -v 0 -n 1 -r -F 25:1 $SUBSAMPLINGMODE | \

     mpeg2enc -f 7 -T 90 -F 3 -np -a 2 -v 0 -o "$MPG"

 fi

 #

 # cleanup

 #

 rm $TMP