add a noise to image edges

coffee-grinder

#!/bin/sh
arg=0
export verbose=0

script_help(){
			echo "Usage: coffee-grinder [OPTIONS]  "
			echo "	-r, --radius 	set edge detection radius (default 2)"
			echo "	-a, --amount 	set noise amount (default 25)"
			echo "	-h, --help 	show this help"
}

verbose_echo(){
if [ $verbose != 0 ]
then
	echo $@
fi
}

while [ -n "$1" ]; do
	case "$1" in
		-a | --amount)
			amount=$2
			shift;;
		-r | --radius)
			blur=$2
			shift;;
		-h | --help)
			script_help 
			exit;;
		-v | --verbose)
			export verbose=1;;
		*)
			case $arg in
				0)
					input=$1
					arg=1;;
				1)
					output="$1"
					arg=2;;
				*)
					echo "Error: Too many arguments"
					script_help
					exit;;
			esac;;
	esac
shift
done

input_filename=$(basename $input)

if [ -z "$amount" ]
then
	amount=25
fi

if [ -z "$blur" ]
then
	blur=2
fi

resx=$(identify "$input" | grep -Po '[0-9]*?(?=(x))' | head -1)
resy=$(identify "$input" | grep -Po '(?<=(x))[0-9]*' | head -1)
keysize=$(calc -p \($resx\*$resy\))
uuid=$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 8 | head -n 1)
tempkey="/tmp/$input_filename.coffee-grinder.$uuid"

umask 066 ; touch $tempkey

verbose_echo "Picture size:     $resx"x"$resy"
verbose_echo "Keysize:  $keysize"
verbose_echo "Input: 	$input"
verbose_echo "Output: 	$output"
verbose_echo "Key Location:     $tempkey"
dd if=/dev/urandom of=$tempkey bs=1 count=$keysize status=none

convert -size $resx\x$resy -depth 8 gray:$tempkey $tempkey.png
rm $tempkey
convert -blur $blur $input bmp:- | composite $input bmp:- -compose difference -channel RGB -colorspace Gray PNG24:- | \
convert png24:- -auto-level -channel RGB +level 0%,$amount% -colorspace Gray png:- | \
convert $tempkey.png png:- -alpha off -compose copy_opacity -composite PNG:- | \
composite -compose linear-light -colorspace srgb $input PNG:- $output
rm $tempkey.png