Geometry library for matlab. Performs geometric computations on points, lines, circles, polygons...
function res = parallelLine(line, point)
%PARALLELLINE Create a line parallel to another one.
% RES = parallelLine(LINE, POINT);
% Returns the line with same direction vector than LINE and going through
% the point given by POINT.
% LINE is given as [x0 y0 dx dy] and POINT is [xp yp].
% RES = parallelLine(LINE, DIST);
% Uses relative distance to specify position. The new line will be
% located at distance DIST, counted positive in the right side of LINE
% and negative in the left side.
% See also:
% lines2d, orthogonalLine, distancePointLine
% author : David Legland
% INRA - TPV URPOI - BIA IMASTE
% created the 31/10/2003.
% 31/07/2005 add usage of distance
% 15/06/2009 change convention for distance sign
if size(point, 1)==1
% use a distance. Compute position of point located at distance DIST on
% the line orthogonal to the first one.
point = pointOnLine([line(:,1) line(:,2) line(:,4) -line(:,3)], point);
% normal case: compute line through a point with given direction
res = zeros(1, 4);
res(1:2) = point;
res(3:4) = line(3:4);