corsinversion.js

(function(a,b,step){
  var increasing = null, decreasing=null,directions={X:-1,Y:-1};
  if(a.X<b.X){
    increasing = 'X';
    decreasing = 'Y';
    directions.X=1;
  }
  if(a.Y<b.Y){
    increasing = 'Y';
    decreasing = 'X';
    directions.Y=1;
  }
  step *= ( b[increasing] - a[increasing] );
  is_good = (function(p){
    return a[increasing]<b[increasing]?p[increasing]<b[increasing]:p[increasing]<b[increasing];
  });
  var p = {X:a.X,Y:a.Y}, inverted_point = {X:0,Y:0};
  inverted_point[increasing] = b[increasing];
  inverted_point[decreasing] = b[decreasing];
  while(is_good(p)){
    console.log("(",p.X,",",p.Y,")::(",inverted_point.X,",",inverted_point.Y,");");
    inverted_point[decreasing]+=step*directions[decreasing];
    p[increasing]+=step*directions[increasing];
  }
})({X:0,Y:30},{X:20,Y:10},2);