% @(#)rebin_spli.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:43:53 
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      rebin_spli.hlq
%.AUTHOR     KB, IPG/ESO
%.KEYWORDS   MIDAS, help files, REBIN/SPLINE
%.PURPOSE    On-line help file for the command: REBIN/SPLINE
%.VERSION    1.0  20-JUL-1991 : Creation, KB
%.VERSION    1.1  09-JAN-1992 : Creation, KB
%----------------------------------------------------------------
\se
SECTION./SPLI
\es\co
REBIN/SPLINE						09-JAN-1992  KB
\oc\su
REBIN/SPLINE in out [stepx,stepy] [offx,offy] [startx,starty]
REBIN/SPLINE in out [refframe]
	rebin an image using cubic splines
\us\pu
Purpose:  
          Do rebinning of an image via cubic splines using new stepsizes and
          start points.
\up\sy
Syntax: 
          REBIN/SPLINE in out [stepx,stepy] [offx,offy] [startx,starty]
          REBIN/SPLINE in out [refframe] 
\ys\pa
          in = input frame
\ap\pa
          out = output frame
\ap\pa
          refframe = optional reference frame; if given, the start (and with
               that the offsets `offx,offy' will be determined) and step values
               for the output frame will be copied from the refframe
\ap\pa
          stepx,stepy = new stepsizes in x,y (in world coordinates); 
\\
               defaulted to 1.,1.
\ap\pa
          offx,offy = absolute offset (in world coordinates) from start in x,y
               of input frame where we begin sampling for the result frame;
\\
               defaulted to 0.,0.
\ap\pa
          startx,starty = new start values (in world coords), if given, these
               values will be stored in descriptor START of result frame
               (but they do not affect the beginning of the sampling, that is
               controlled by `offx,offy');
\\
               otherwise, descriptor START of the input frame + the offsets
               described above will determine the new values of START
\ap\no
Note:  
          In MIDAS the following convention is used:
\\
          World coordinate values (e.g. start values) are related to the
          center of the pixels!
\\
          So, if you have e.g. start values 12.4, 4.8 and stepsize 1.4, 1.4 in
          a frame, the left and right edges of the first pixel (seen as a small
          plane) would be at 11.7 and 13.1 and the lower and upper edge at
          4.1 and 5.5, respectively. The center of the first sampled pixel
          would be at 12.4+`offx',4.8+`offy'.
\\
          Pixels in the result frame sampled outside the input frame are set to
          the null value stored in real keyword NULL(2); the no. of pixels set
          to null will be stored in NULL(1). You can start sampling outside
          the input frame by specifying the offsets accordingly.
\on\sa
See also:
          REBIN/LINEAR, REBIN/ROTATE, REBIN/II, REBIN/IT, REBIN/TI, REBIN/TT,
\\
          READ/DESCR, WRITE/DESCR
\as\exs
Examples:
\ex
          REBIN/SPLINE conejo tortuga 0.3,.9
           Let us assume that the frame `conejo.bdf' has start = 0.0,0.0 and
           step = 1.0,1.0.
\\
           Then we rebin it with stepsizes 0.3 in x- and 0.9 in y-direction,
           we start sampling with the first pixel in x and y of
           `conejo.bdf', keep same start values and store results in frame
           `tortuga.bdf', the result frame has more pixels than `conejo.bdf'.
\xe\ex
          REBIN/SPLINE conejo tortuga 0.3,0.9 1.0,3.3
           As above but start sampling at pixel with has center 1.0 and 3.3,
           therefore `tortuga.bdf' will have less pixels than in the ex. above.
           Descriptor START of tortuga will be 1.0,3.3 (0.0+1.0,0.0+3.3).
\xe\ex
          REBIN/SPLINE conejo tortuga 0.3,0.9 1.,3.3 401.3,-20.8
           As above but descr. START of `tortuga.bdf' will contain 401.3,-20.8 ;
           the data will be exactly the same.
\xe\ex
          REBIN/SPLINE conejo pajaro mariposa
           Let us assume that the frame `mariposa.bdf' has start = 1.2,1.8 and
           step = 0.6,0.6.
\\
           Then we rebin `conejo.bdf' with stepsizes 0.6 in x- and
           y-direction.
\\
           We start sampling with the pixel the center of which is located
           at 1.2 and 1.8. Store results in frame `pajaro.bdf'.
\xe \sxe