Pixel-perfect javascript 2D collision detection

collision.js

/*

2d pixel-perfect collision detection

Requires that each object has a rectangular bounding box (simple x/y/w/h, no rotation)
and a bit mask (i.e. an array of lines and columns containing 0s for empty pixels and 1s for solid pixels).

On each frame of the animation, take all pairs of objects and
1. compare the bounding boxes
2. for those that collide, check for overlayed bits by creating a new mask that is the AND of the 2 sub-masks and check for 1s

*/

// Example with a predefined (simplistic) pair of objects
var object1 = {
  x: 0,
  y: 0,
  w: 8,
  h: 4,
  mask : [
    [0,0,0,1,1,0,0,0],
    [0,0,1,1,1,1,0,0],
    [0,1,1,1,1,1,1,0],
    [1,1,1,1,1,1,1,1]
  ]
};

var object2 = {
  x: 8,
  y: 2,
  w: 8,
  h: 4,
  mask : [
    [0,1,1,1,1,0,0,0],
    [0,1,1,1,1,0,0,0],
    [0,1,1,1,1,0,0,0],
    [1,1,1,1,1,1,1,1]
  ]
};

function collide(o1, o2) {
  var xs = [o1, o2].sort(function(a, b) {return o1.x - o2.x;});
  var ys = [o1, o2].sort(function(a, b) {return o1.y - o2.y;});
  
  // Do bounding boxes collide
  if(xs[0].x + xs[0].w > xs[1].x && ys[0].y + ys[0].h > ys[1].y) {
    // Create the collision bounding box
    var cBounding = {};
    cBounding.x = xs[1].x;
    cBounding.y = ys[1].y;
    cBounding.w = Math.min(xs[0].x + xs[0].w, xs[1].x + xs[1].w) - cBounding.x;
    cBounding.h = Math.min(ys[0].y + ys[0].h, ys[1].y + ys[1].h) - cBounding.y;
    
    // Overlay the 2 masks within the collision bounding box and return as soon as a 1 is found
    for(var x = 0; x < cBounding.w; x ++) {
      for(var y = 0; y < cBounding.h; y ++) {
        var bit1 = o1.mask[y + cBounding.y - o1.y][x + cBounding.x - o1.x];
        var bit2 = o2.mask[y + cBounding.y - o2.y][x + cBounding.x - o2.x];
        if(bit1 && bit2) {
          return {
            x : x + cBounding.x,
            y : y + cBounding.y
          };
        }
      }
    }
  }
};

console.log(collide(object1, object2));

What if the velocity of the player is greater than the size (width or height) of the box?