% @(#)zoom_chan.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:44:04 
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      zoom_chan.hlq
%.AUTHOR     KB, IPG/ESO
%.KEYWORDS   MIDAS, help files, ZOOM/CHANNEL
%.PURPOSE    On-line help file for the command: ZOOM/CHANNEL
%.VERSION    1.0  30-APR-1990 : Creation, KB
%----------------------------------------------------------------
\se
SECTION./CHAN
\es\co
ZOOM/CHANNEL						30-APR-1990  KB
\oc\su
ZOOM/CHANNEL [zoom_fact] [center]
	zoom image on image display
\us\pu
Purpose: 
          Zoom image on image display.
\up\sy
Syntax: 
          ZOOM/CHANNEL [zoom_fact] [center]
\ys\pa
          zoom_fact = integer zoom factor;
\\
              if zoom_fact is omitted, zoom the image on image display according
              to size of rectangle formed by the two cursors (a);
\\
              maximum of the zoom factors in x and y is taken, so that equal
              magnification in x and y is assured;
\\
              if zoom factor is given, zoom the image with explicit zoom factor
              in interval [1,32] (b);
\\
              if zoom_factor = UP or DOWN (c), zoom up or down continuously:
\\
              every time the ENTER button is pressed the image is zoomed with
              the next higher (lower) zoom factor;
\\
              control returns to the terminal when highest (=32) or lowest (=1)
              zoom factor is reached, or if EXIT button is pressed;
\\
              defaulted to option (a)
\ap\pa
          center = only for option (b) above: 
\\
              x,y-screen coords. of center pixel for zooming;
\\
              if center is omitted, use cursor to choose center of zoom
\ap\sa
See also:
          CLEAR/ZOOM, ZOOM/OVERLAY, GET/CURSOR, VIEW/IMAGE
\as\no
Note:   
          For all options (except (b) with explicit center values) you have
          to press the ENTER button to actually zoom. For option (a) the center
          of zoom is the center of the cursor rectangle otherwise the single
          cursor indicates the center.
\\
          Zooming is done in such a way that the zoom center pixel remains at
          the same spot (approximately).
\on\exs
Examples:
\ex
          ZOOM/CHANNEL
            Modify size of cursor rectangle to determine the zoom factor and 
            move it over the part of the image which should remain on display, 
            press ENTER to magnify the image.
\xe\ex
          ZOOM/CHANNEL 4 
            Move cursor to pixel of which the position should remain fixed on 
            display, press ENTER to magnify image by a factor of 4.
\xe\ex
          ZOOM/CHANNEL 4 44,102
            Zoom image by a factor of 4, pixel at screen coordinates (44,102)
            remains (approx.) at same place on display.
\xe \sxe