imageResize

#!/bin/sh
#
# Uses ImageMagick to downsize images
#
# Accepts: 	png, jpg, jpeg, gif
# Outputs: 	png
# Usage: 	./imageResize WIDTH HEIGHT FILENAME
# Ex:		./imageResize 320 480 image.png
# 
# Latest Test Environment
# OSX:			10.12.3
# ImageMagick:	7.0.5-4 Q16 x86_64
# 


# =====================================
# ==========[ Library Check ]==========
# =====================================

command -v convert >/dev/null 2>&1 || { 
	echo >&2 'Error: cannot find "convert" command.... Is ImageMagick installed?'; 
	exit 1; 
}

# ================================================
# ==========[ Arguments Validity Check ]==========
# ================================================

if [ "$#" -ne 3 ]; then
	echo "Error: Incorrect number of arguments ($#). Needs to be 3."
	echo "Usage: imageResize WIDTH HEIGHT FILENAME"
	echo "Example: imageResize 360 480 test.png"

	exit 1
fi

width=$1
height=$2
filePath=$3

numRegExp='^[0-9]+$'
if ! [[ $width =~ $numRegExp ]] ; then
	echo "Error: Width is not a valid number" >&2
	exit 1
fi
if ! [[ $height =~ $numRegExp ]] ; then
	echo "Error: Height is not a valid number" >&2
	exit 1
fi

if [ ! -f "$filePath" ]; then
	echo "File ($filePath) not found!"
	exit 1
fi

fileFullName=`echo $filePath|grep -i ".png\|.jpg\|.jpeg\|.gif\|.tiff"`
if [ ! -n "$fileFullName" ] ; then
	echo "File not a valid format (png,jpg,jpeg,gif,tiff)"
	exit 1
fi
	

# ==========================================
# ==========[ Converting Process ]==========
# ==========================================

echo "File: \t\t"$fileFullName
echo "Resolution:\t""$width""x""$height"
printf "Converting:\t...."

fileName="${fileFullName%.*}"
fileExt="${fileFullName##*.}"


# 1/3 - Strip(reconvert) non-standard PNG (Left by amazing Photoshop.)
if [ $fileExt == "png" ] ; then
	convert "$fileFullName" -strip "$fileFullName"
fi

# 2/3 - The actual conversion
convert "$fileName"".""$fileExt" -resize "$width""x""$height"\> "$fileName"".png"

# 3/3 - Cleanup - Original PNGs are overwritten. Remove anything not originally PNG format
if [ $fileExt != "png" ] ; then
	rm $fileFullName
fi

echo " Done!"