d3.geom.contour = function()

in pytheas-core/src/main/resources/js/d3/d3.geom.js [12:55]

• 36 lines of code
• 14 McCabe index (conditional complexity)

d3.geom.contour = function(grid, start) {
  var s = start || d3_geom_contourStart(grid), // starting point
      c = [],    // contour polygon
      x = s[0],  // current x position
      y = s[1],  // current y position
      dx = 0,    // next x direction
      dy = 0,    // next y direction
      pdx = NaN, // previous x direction
      pdy = NaN, // previous y direction
      i = 0;

  do {
    // determine marching squares index
    i = 0;
    if (grid(x-1, y-1)) i += 1;
    if (grid(x,   y-1)) i += 2;
    if (grid(x-1, y  )) i += 4;
    if (grid(x,   y  )) i += 8;

    // determine next direction
    if (i === 6) {
      dx = pdy === -1 ? -1 : 1;
      dy = 0;
    } else if (i === 9) {
      dx = 0;
      dy = pdx === 1 ? -1 : 1;
    } else {
      dx = d3_geom_contourDx[i];
      dy = d3_geom_contourDy[i];
    }

    // update contour polygon
    if (dx != pdx && dy != pdy) {
      c.push([x, y]);
      pdx = dx;
      pdy = dy;
    }

    x += dx;
    y += dy;
  } while (s[0] != x || s[1] != y);

  return c;
};