Liang-Barsky line clipping

liang-barsky.js

/**
 * Liang-Barsky function by Daniel White 
 * 
 * @link http://www.skytopia.com/project/articles/compsci/clipping.html
 *
 * @param  {number}        x0
 * @param  {number}        y0
 * @param  {number}        x1
 * @param  {number}        y1
 * @param  {array<number>} bbox
 * @return {array<array<number>>|null}
 */
function liangBarsky (x0, y0, x1, y1, bbox) {
  var [xmin, xmax, ymin, ymax] = bbox;
  var t0 = 0, t1 = 1;
  var dx = x1 - x0, dy = y1 - y0;
  var p, q, r;

  for(var edge = 0; edge < 4; edge++) {   // Traverse through left, right, bottom, top edges.
    if (edge === 0) { p = -dx; q = -(xmin - x0); }
    if (edge === 1) { p =  dx; q =  (xmax - x0); }
    if (edge === 2) { p = -dy; q = -(ymin - y0); }
    if (edge === 3) { p =  dy; q =  (ymax - y0); }

    r = q / p;

    if (p === 0 && q < 0) return null;   // Don't draw line at all. (parallel line outside)

    if(p < 0) {
      if (r > t1) return null;     // Don't draw line at all.
      else if (r > t0) t0 = r;     // Line is clipped!
    } else if (p > 0) {
      if(r < t0) return null;      // Don't draw line at all.
      else if (r < t1) t1 = r;     // Line is clipped!
    }
  }

  return [
    [x0 + t0 * dx, y0 + t0 * dy],
    [x0 + t1 * dx, y0 + t1 * dy]
  ];
}

worked like a charm, thanks!

@ashleedawg check this one out https://github.com/w8r/liang-barsky