Bash: space in variable value later used as parameter

Question

While writing a bash script to help creating polaroid thumbnail using Imagick\'s convert commmand. I encounter a problem. Although, I manage to work around with

Answer 1

CAPTION="$1"
IN_FILE="resources/puppy.png"
OUTFILE="resources/puppy_polaroid.png"

case "$CAPTION" in
  "" ) CAPTION="-caption ''";;
  * ) CAPTION='-caption "$CAPTION"';;
esac

convert $CAPTION "$IN_FILE" "$OUTFILE"