Help for NORANGLE

PURPOSE
    A routine to compute the angular rotation from the line,sample termini
of a line within an image and return the angle in degrees and radians from
the top of the picture clockwise. If the rotation is anticlockwise the
values are returned as a negative number. 

    Note that this angle is a vector and the angle's sign is dependent
on the line origin and its terminus.


OPERATION

Internally, the program computes the arctangent of the height and width of
a triangle described by the line,sample coordinates of the straight line.

A transformation of raster coordinates to cartesian coordinates has to
be performed according to:

       raster (1,1) -> Cartesian ((-w/2)+1,(h/2)+1)
       raster (w,1) -> Cartesian ((w/2)+1,(h/2)+1)
       raster (1,h) -> Cartesian ((-w/2)+1,(-h/2)+1)
       raster (w,h) -> Cartesian ((w/2)+1,(-h/2)+1)

       Based on that, the formula 
       x = rasterX - (w/2) + 1
       y = (h/2) + 1 - rasterY

       where w is width of triange and h is its height

       Thus, you obtain x1,y1 and x2,y2

       the angle (in radians) is computed from

        arctangent (y1-y2/x1-x2) 


OUTPUT

    Four parameters are output in TCL variables
    DEGREES = Angle, in degrees
    RADIANS = Angle, in radians
    HEIGHT  = Height, in pixels of the inscribed triangle
    WIDTH   = Width, in pixels of the inscribed triangle



HISTORY

  2012-10-25 R.J. Bambery - Initial Release  
  2012-11-16 R.J. Bambery - Change name to norangle            
  2015-12-10 W.L. Bunch - Migrated to MIPL
  2022-07-26 B. Crocco - afids to opensource