function geo_bbox(transform, cylindrical_proj) {
let w = 900;
let h = 530;
let lower_left_x = -transform.x / transform.k;
let lower_left_y = (h - transform.y) / transform.k;
let upper_right_x = (w - transform.x) / transform.k;
let upper_right_y = -transform.y / transform.k;
let lower_left = [lower_left_x, lower_left_y];
let upper_right = [upper_right_x, upper_right_y];
let geo_lower_left = cylindrical_proj.invert(lower_left);
let geo_upper_right = cylindrical_proj.invert(upper_right);
return [...geo_lower_left, ...geo_upper_right];
}