SECTION./CTRA
EXTRACT/CTRACE [step] [frame] [plot_flag] [zw_option]
	extract a column from displayed image
SECTION./CURS
EXTRACT/CURSOR [subfr] [xpx,ypx] [loop_flag]
	extract a subframe via cursor
SECTION./IMAG
EXTRACT/IMAGE out = in intval
EXTRACT/IMAGE out = in center_spec loff roff
	extract a subimage from an image frame
SECTION./LINE
EXTRACT/LINE out = in[..] step
	extract a 1-dim line from a 2-dim frame
SECTION./REFE
EXTRACT/REFERENCE_IMAGE in ref out low[,hi] [inout_flag]
	extract subimage according to reference image
SECTION./ROTA
EXTRACT/ROTATED_IMAGE steps frame
	extract a rotated subimage from displayed image
SECTION./RTRA
EXTRACT/RTRACE [step] [frame] [plot_flag] [zw_option]
	extract a row from displayed image
SECTION./SLIT
EXTRACT/SLIT [in_option] [resframe] [slit_specs]
	extract a subimage defined by a fixed slit from image
SECTION./TRAC
EXTRACT/TRACE [step] [frame] [plot_flag] [cut_option] [zw_option]
	extract a line from displayed image
