Converting Images from Android xhdpi to Iphone 1x And 2x

ConvertImageToIphoneSize

#!/bin/bash

# Script's goals
#
# 1 - Trim image
# 2 - Create folder for exported ones
# 3 - Convert proportionally
#

# Script usage
#
# ConvertImageToIphoneSize file.png 720 (Obs.: I'm using XHDPI value just to exemplify how to use it)
# ConvertImageToIphoneSize . 720 (Obs.: it'll take every single png file on that folder)
#

# References to build it
#
# http://www.unix.com/shell-programming-scripting/42170-function-returns-string.html
# http://stackoverflow.com/a/965072/832748
# http://www.imagemagick.org/Usage/resize/
# http://stackoverflow.com/questions/59838/how-to-check-if-a-directory-exists-in-a-shell-script
# http://stackoverflow.com/questions/4665051/check-if-passed-argument-is-file-or-directory-in-bash
# http://stackoverflow.com/questions/242538/unix-shell-script-find-out-which-directory-the-script-file-resides

# Functions used on this script

function ruleOfThree(){
 A=$1
 B=$2
 C=$3
 BC=`expr $C \* $B`
 X=`expr $BC / $A`
 echo $X
}

function convertToIphoneImages(){
	# Goal - 1 - Trim image
	PWD=$(pwd)
	PWD=$(printf %q "$PWD")
	
	NAME=${1}
	if [ ${1:2} = "./" ] ; then
		NAME=${1:2}
	fi	
	NAME=$(printf %q "$NAME")
	
	FULLPATHFILE=$PWD/$NAME
	
	eval convert "$FULLPATHFILE" -trim "$FULLPATHFILE"	
	
	# Getting parameters to be used on conversion process 
	RESOLUTION=$2
	WIDTHORIGINAL=$(eval identify -format "%w" "$FULLPATHFILE"  | sed 's,^ *,,; s, *$,,')
	
	WIDTHIPHONE1X=$(ruleOfThree $RESOLUTION $WIDTHORIGINAL 320)
	WIDTHIPHONE2X=$(ruleOfThree $RESOLUTION $WIDTHORIGINAL 640)
	
	#Separating Filename from extension
	FILENAME=$(basename "$FULLPATHFILE")
	EXTENSION="${FILENAME##*.}"
	FILENAME="${FILENAME%.*}"
	
	# Goal - 2 - Create folder for exported ones
	if [ ! -d "$PWD/exported" ] ; then
		mkdir -pv "$(pwd)/exported"
	fi
	
	# Goal - 3 - Convert proportionally
	eval convert "$FULLPATHFILE" -resize $WIDTHIPHONE1X "$PWD/exported/$FILENAME.$EXTENSION"
	eval convert "$FULLPATHFILE" -resize $WIDTHIPHONE2X "$PWD/exported/$FILENAME@2x.$EXTENSION"
}

if [ -d "$1" ]; then	
	
	for dir in $1/*.png
	do
	    dir=${dir%*/}
	    echo Processing ${dir##*/}
	    convertToIphoneImages "$dir" $2
	done	

elif [ -f "$1" ]; then
	echo Processing "$1"
	convertToIphoneImages "$1" $2
else
    echo "it's not a valid (path|file)"
    exit 1
fi