#!/usr/bin/env bash

# pdfScale.sh
#
# Scale PDF to specified percentage of original size.
#
# Gutavo Arnosti Neves - 2016 / 07 / 10
#
# This script: https://github.com/tavinus/pdfScale
#    Based on: http://ma.juii.net/blog/scale-page-content-of-pdf-files
#         And: https://gist.github.com/MichaelJCole/86e4968dbfc13256228a


VERSION="1.0.7"
SCALE="0.95"               # scaling factor (0.95 = 95%, e.g.)
VERBOSE=0                  # verbosity Level
BASENAME="$(basename $0)"  # simplified name of this script
GSBIN=""                   # Set with which after we check dependencies
BCBIN=""                   # Set with which after we check dependencies

LC_MEASUREMENT="C"         # To make sure our numbers have .decimals
LC_ALL="C"                 # Some languages use , as decimal token
LC_CTYPE="C"
LC_NUMERIC="C"

printVersion() {
	if [[ $1 -eq 2 ]]; then
		echo >&2 "$BASENAME v$VERSION"
	else
		echo "$BASENAME v$VERSION"
	fi
}

printHelp() {
	printVersion
	echo "
Usage: $0 [-v] [-s <factor>] <inFile.pdf> [outfile.pdf]
       $0 -h
       $0 -V

Parameters:
 -v          Verbose mode, prints extra information
             Use twice for even more information
 -h          Print this help to screen and exits
 -V          Prints version to screen and exits
 -s <factor> Changes the scaling factor, defaults to 0.95
             MUST be a number bigger than zero. 
             Eg. -s 0.8 for 80% of the original size 

Notes:
 - Options must be passed before the file names to be parsed
 - The output filename is optional. If no file name is passed
   the output file will have the same name/destination of the
   input file, with .SCALED.pdf at the end (instead of just .pdf)
 - Having the extension .pdf on the output file name is optional,
   it will be added if not present
 - Should handle file names with spaces without problems
 - The scaling is centered and using a scale bigger than 1 may
   result on cropping parts of the pdf.

Examples:
 pdfScale myPdfFile.pdf
 pdfScale myPdfFile.pdf myScaledPdf
 pdfScale -v -v myPdfFile.pdf
 pdfScale -s 0.85 myPdfFile.pdf myScaledPdf.pdf
 pdfScale -v -v -s 0.7 myPdfFile.pdf
 pdfScale -h
"
}

usage() { 
	printVersion 2
	echo >&2 "Usage: $0 [-v] [-s <factor>] <inFile.pdf> [outfile.pdf]"
	echo >&2 "Try:   $0 -h # for help"
	exit 1
}

vprint() {
	[[ $VERBOSE -eq 0 ]] && return 0
	timestamp=""
	[[ $VERBOSE -gt 1 ]] && timestamp="$(date +%Y-%m-%d:%H:%M:%S) | "
	echo "$timestamp$1"
}

printDependency() {
	printVersion 2
	echo >&2 $'\n'"ERROR! You need to install the package '$1'"$'\n'
	echo >&2 "Linux apt-get.: sudo apt-get install $1"
	echo >&2 "Linux yum.....: sudo yum install $1"
	echo >&2 "MacOS homebrew: brew install $1"
	echo >&2 $'\n'"Aborting..."
	exit 3
}

parseScale() {
	if ! [[ -n "$1" && "$1" =~ ^-?[0-9]*([.][0-9]+)?$ && (($1 > 0 )) ]] ; then
		echo >&2 "Invalid factor: $1"
		echo >&2 "The factor must be a number between 0 and 1."
		echo >&2 "Example: for 80% use 0.8"
		exit 2
	fi
	SCALE=$1
}


getPageSize() {
	# get MediaBox info from PDF file using cat and grep, these are all possible
	# /MediaBox [0 0 595 841]
	# /MediaBox [ 0 0 595.28 841.89]
	# /MediaBox[ 0 0 595.28 841.89 ]
	local mediaBox="$(cat "$INFILEPDF" | grep -a '/MediaBox')" # done with externals
	findex=$(expr index "$mediaBox" "0")    # Find first Zero
	findex=$(($findex+3))                   # Adjust postion to 1st number
	mediaBox="${mediaBox:$findex}"          # Re-set base string
	findex=$(expr index "$mediaBox" ' ')    # Tokenize
	PGWIDTH=$(printf '%.0f' "${mediaBox:0:(($findex-1))}")  # Get Round Width
	mediaBox="${mediaBox:$findex}"          # Re-set base string
	findex=$(expr index "$mediaBox" ' ')    # Ends with space or ]
	[[ $findex -eq 0 ]] && findex=$(expr index "$mediaBox" ']')
	PGHEIGHT=$(printf '%.0f' "${mediaBox:0:(($findex-1))}") # Get Round Height
	vprint "         Width: $PGWIDTH postscript-points"
	vprint "        Height: $PGHEIGHT postscript-points"
}

while getopts ":vhVs:" o; do
    case "${o}" in
        v)
            ((VERBOSE++))
            ;;
        h)
            printHelp
            exit 0
            ;;
        V)
            printVersion
            exit 0
            ;;
        s)
            parseScale ${OPTARG}
            ;;
        *)
            usage
            ;;
    esac
done
shift $((OPTIND-1))

vprint "$(basename $0) v$VERSION - Verbose execution"

# Dependencies
vprint "Checking dependencies"
command -v gs >/dev/null 2>&1 || printDependency 'ghostscript'
command -v bc >/dev/null 2>&1 || printDependency 'bc'

GSBIN=$(which gs 2>/dev/null)
BCBIN=$(which bc 2>/dev/null)

vprint "  Scale factor: $SCALE"

# Validate args
[[ $# -lt 1 ]] && { usage; exit 1; }
INFILEPDF="$1"
[[ "$INFILEPDF" =~ ^..*\.pdf$ ]] || { usage; exit 2; }
vprint "    Input file: $INFILEPDF"

# Parse output filename
if [[ -z $2 ]]; then
	OUTFILEPDF="${INFILEPDF%.pdf}.SCALED.pdf"
else
	OUTFILEPDF="${2%.pdf}.pdf"
fi
vprint "   Output file: $OUTFILEPDF"

# Set PGWIDTH and PGHEIGHT
getPageSize

# Compute translation factors (to center page.
XTRANS=$(echo "scale=6; 0.5*(1.0-$SCALE)/$SCALE*$PGWIDTH" | "$BCBIN")
YTRANS=$(echo "scale=6; 0.5*(1.0-$SCALE)/$SCALE*$PGHEIGHT" | "$BCBIN")
vprint " Translation X: $XTRANS"
vprint " Translation Y: $YTRANS"

# Do it.
"$GSBIN" \
-q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -dSAFER \
-dCompatibilityLevel="1.5" -dPDFSETTINGS="/printer" \
-dColorConversionStrategy=/LeaveColorUnchanged \
-dSubsetFonts=true -dEmbedAllFonts=true \
-dDEVICEWIDTH=$PGWIDTH -dDEVICEHEIGHT=$PGHEIGHT \
-sOutputFile="$OUTFILEPDF" \
-c "<</BeginPage{$SCALE $SCALE scale $XTRANS $YTRANS translate}>> setpagedevice" \
-f "$INFILEPDF"