#!/bin/sh

## Some JPEG options
# -sDEVICE=jpeg
# -dUseCIEColor
# -dJPEGQ=100
# -r300
# -dTextAlphaBits=4
# -dGraphicsAlphaBits=4
# -dMaxStripSize=8192

_usage () {
	cat <<EOF
Usage: ${1##*/} [OPTIONS] PDFFILES

All PDF files will be compressed to a PDF file with "-compressed" appended in its name.

Options:

  -c:  Compress raster graphics at the expense of a quality loss.
  -f:  Overwrite existing files.
  -h:  Show this help.
  -i:  In-place compression.
  -n:  Do not compress raster graphics at all. Output size is usually greater.

For more details:

  $ gs -sDEVICE=pdfwrite -o /dev/null \\
    -c "currentpagedevice { exch ==only ( ) print == } forall"

  http://partners.adobe.com/public/developer/en/acrobat/sdk/pdf/pdf_creation_apis_and_specs/DistillerParameters.pdf

EOF
}

OPT_INPLACE=false
OPT_OVERWRITE=false
OPT_COMPRESSION="-dColorConversionStrategy=/LeaveColorUnchanged -dDownsampleMonoImages=false -dDownsampleGrayImages=false -dDownsampleColorImages=false -dAutoFilterColorImages=false -dAutoFilterGrayImages=false -dColorImageFilter=/FlateEncode -dGrayImageFilter=/FlateEncode"

while getopts ":cfhin" opt; do
	case $opt in
	c)
		OPT_COMPRESSION="" ;;
	f)
		OPT_OVERWRITE=true ;;
	h)
		_usage "$0"
		exit 1 ;;
	i)
		OPT_INPLACE=true ;;
	n)
		OPT_COMPRESSION="-dColorConversionStrategy=/LeaveColorUnchanged -dEncodeColorImages=false -dEncodeGrayImages=false -dEncodeMonoImages=false" ;;
	\?)
		_usage "$0"
		exit 1 ;;
	esac
done

shift $(($OPTIND - 1))

if [ $# -eq 0 ]; then
	_usage "$0"
	exit 1
fi

for i ; do

	if [ ! -f "$i" ]; then
		echo "$i is not a valid file."
		continue
	fi

	case "$i" in
	*/*) ;;
	*)   i="./$i" ;;
	esac
	DIRNAME="${i%/*}"
	BASENAME="${i##*/}"
	EXTNAME="${BASENAME##*.}"
	BASENAME="${BASENAME%.*}"
	OUTPUT="$DIRNAME/$BASENAME-compressed.pdf"
	if [ -e "$OUTPUT" ] && ! $OPT_OVERWRITE; then
		echo "$OUTPUT alredy present. Skipping."
		continue
	fi

	echo "$i"

	gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite $OPT_COMPRESSION -sOutputFile="$OUTPUT" "$i"
	if $OPT_INPLACE; then
		rm -f "$i"
		mv "$OUTPUT" "$i"
	fi
done