Don't worry! It's only stuff...

#!/bin/bash
 
# get image name
if [ -z $1 ]; then
	# read from dialog
	INPUT=$(zenity --title  "Etope-O-Mat" --entry --text "Bildname:")
else
	# copy input from command line
	INPUT=$@
fi
 
for IMAGE in $INPUT; do
	# convert image name to lower case
	IMAGE=$(echo ${IMAGE} | tr "[:upper:]" "[:lower:]")
 
	# add .jpg file extension if not already exists
	IMAGE="${IMAGE/.jpg}.jpg"
 
	# set input and output
	PATH_IN=/media/bilder/300dpi
	PATH_OUT=/home/$USER/200px
	FILE_IN="${PATH_IN}/${IMAGE}"
	FILE_OUT="${PATH_OUT}/${IMAGE}"
 
	# check dirs
	[ ! -d $PATH_OUT ] && mkdir $PATH_OUT
 
	# convert image
	if [ -f $FILE_IN ]; then
		convert $FILE_IN -resize "200x200>" -size 200x200 xc:white +swap -gravity center -composite $FILE_OUT
	else
		zenity --info --title "Datei nicht gefunden" --text "Die Datei $IMAGE konnte nicht gefunden werden"
	fi
done | zenity --auto-close --progress --title="Etope-O-Mat" --text="Bearbeite $IMAGE..."