convert pdf file from RGB to CYMK using ghost script

gs_rgb2cymk

#!/usr/bin/bash
help(){
    echo "Usage: $0 <input.pdf> <output.pdf> [safe]"
    echo "optional \`safe\` option, preform less processing, possibly better quality with a much larger file size."
    exit 127
}

if [[ $1 == "" ]] ; then
    echo "Missing parameter input pdf file"
    help
elif [[ $2 == "" ]] ; then
    echo "Missing parameter output pdf file"
    help
fi

case $3 in
    "safe")
        gs -dSAFER -dBATCH -dNOPAUSE -dNOCACHE -sDEVICE=pdfwrite -dAutoRotatePages=/None -sColorConversionStrategy=CMYK -dProcessColorModel=/DeviceCMYK -dAutoFilterColorImages=false -dAutoFilterGrayImages=false -dColorImageFilter=/FlateEncode -dGrayImageFilter=/FlateEncode -dDownsampleMonoImages=false -dDownsampleGrayImages=false -sOutputFile="$2" "$1"
    ;;
    "")
        gs -dSAFER -dBATCH -dNOPAUSE -dNOCACHE -sDEVICE=pdfwrite -dAutoRotatePages=/None -sColorConversionStrategy=CMYK -dProcessColorModel=/DeviceCMYK -sOutputFile="$2" "$1"
    ;;
    *)
        echo "Unknown parameter \`$3\`"
        help
    ;;
esac