#compdef pnmscale

local scale

if [[ "$words[2]" = -* ]]; then
  scale=()
else
  scale=( ':scale factor:' )
fi

_arguments '-xsize:width:'  '-width:width:' \
           '-ysize:height:' '-height:height:' \
	   '-xscale:horizontal scale factor:' \
	   '-yscale:horizontal scale factor:' \
	   '-xysize:width::height:' "$scale[@]" \
	   ':file: _pbm_file'