linear_warp

 ==============================================================
 LINEAR_WARP: Apply a linear warp to the points.

 Code written by Katherine Smith, 2003

    GENERAL

      linear_warp(points, lo, hi, ref_lo, ref_hi)

    INPUT/S

      -points:
           The points before warping

      -lo:
           ?

      -hi:
           ?

      -ref_lo:
           ?

      -ref_hi:
           ?
           
    OUTPUT/S

      -points:
           The points after warping

    PENDING WORK

      -

    KNOWN BUG/S

      -None.

    COMMENT/S

      -

    RELATED FUNCTION/S

      POOR_LINEAR_WARP

    ABOUT

      -Created:     November 23rd, 2003
      -Last update: Novermber 25th, 2003
      -Revision:    0.0.2
      -Author:      R. S. Schestowitz, University of Manchester
 ==============================================================

0001 function points = linear_warp(points, lo, hi, ref_lo, ref_hi)
0002 % ==============================================================
0003 % LINEAR_WARP: Apply a linear warp to the points.
0004 %
0005 % Code written by Katherine Smith, 2003
0006 %
0007 %    GENERAL
0008 %
0009 %      linear_warp(points, lo, hi, ref_lo, ref_hi)
0010 %
0011 %    INPUT/S
0012 %
0013 %      -points:
0014 %           The points before warping
0015 %
0016 %      -lo:
0017 %           ?
0018 %
0019 %      -hi:
0020 %           ?
0021 %
0022 %      -ref_lo:
0023 %           ?
0024 %
0025 %      -ref_hi:
0026 %           ?
0027 %
0028 %    OUTPUT/S
0029 %
0030 %      -points:
0031 %           The points after warping
0032 %
0033 %    PENDING WORK
0034 %
0035 %      -
0036 %
0037 %    KNOWN BUG/S
0038 %
0039 %      -None.
0040 %
0041 %    COMMENT/S
0042 %
0043 %      -
0044 %
0045 %    RELATED FUNCTION/S
0046 %
0047 %      POOR_LINEAR_WARP
0048 %
0049 %    ABOUT
0050 %
0051 %      -Created:     November 23rd, 2003
0052 %      -Last update: Novermber 25th, 2003
0053 %      -Revision:    0.0.2
0054 %      -Author:      R. S. Schestowitz, University of Manchester
0055 % ==============================================================
0056 
0057 image_width = max(points); 
0058           % get the maximum of points. Why is that width??
0059 if ((hi - lo)<=0) 
0060   disp('Invalid values of high and low. Low must be lower than high');
0061   return; % break out of function
0062 end
0063 % Smith: line up the edge points, do linear stretch in between!
0064 
0065 % RSS: The following 3 sections are quite mysterious. They implement
0066 %      a warp in some way.
0067 
0068 % Smith: first section - between 1 and lo
0069 %scale_factor1 = (ref_lo-1)/(lo-1);
0070 scale_factor1 = (lo-1)/(ref_lo-1);
0071 points(1:ref_lo,:) = (points(1:ref_lo,:)-1)*scale_factor1 + 1;
0072 
0073 % Smith: second section
0074 scale_factor2 = (hi - lo)/(ref_hi-ref_lo);
0075 points(ref_lo+1:ref_hi-1,:) = (points(ref_lo+1:ref_hi-1,:) - ref_lo)*scale_factor2 + lo;
0076 %scale_factor2 = (ref_hi - ref_lo)/(hi-lo);
0077 %points(:,lo+1:hi-1) = (points(:,lo+1:hi-1) - lo)*scale_factor2 + ref_lo;
0078 
0079 % Smith: third section
0080 scale_factor3 = (image_width-hi)/(image_width-ref_hi);
0081 points(ref_hi:image_width,:) = ...
0082   (points(ref_hi:image_width,:) - ref_hi)*scale_factor3 + hi;
0083 %scale_factor3 = (image_width-ref_hi)/(image_width-hi);
0084 %points(:,hi:image_width) = ...
0085 %  (points(:,hi:image_width) - hi)*scale_factor3 + ref_hi;