module MapProject

Constants

FACTOR_TO_DEG
FACTOR_TO_RAD
GOOGLE_MAPS_MAX_LAT
GOOGLE_MAPS_MAX_LONG
LN2
PIXEL_PER_DEG
PIXEL_PER_RAD
TILE_SIZE
VERSION
WORLD_PX
ZERO_ZERO_PX
ZOOM_MAX

Public Instance Methods

get_bounds_zoom_level(bounds, viewport_w, viewport_h) click to toggle source

Get the zoom level for a viewport given latlng boundary

# File lib/map_project.rb, line 8
def get_bounds_zoom_level(bounds, viewport_w, viewport_h)
  ne = bounds[:ne]
  sw = bounds[:sw]
  lat_fraction = (lat_rad(ne[0]) - lat_rad(sw[0])) / Math::PI
  lng_diff = ne[1] - sw[1]
  lng_fraction = ((lng_diff < 0) ? (lng_diff + 360) : lng_diff) / 360
  lat_zoom = zoom(viewport_h, WORLD_PX, lat_fraction)
  lng_zoom = zoom(viewport_w, WORLD_PX, lng_fraction)
  [[lat_zoom, lng_zoom].min, ZOOM_MAX].min
end

lat_rad(lat) click to toggle source

# File lib/map_project.rb, line 19
def lat_rad(lat)
  sin = Math.sin(Rational(lat * Math::PI, 180))
  rad_x2 = Math.log((1 + sin) / (1 - sin)) / 2
  [[rad_x2, Math::PI].min, -Math::PI].max / 2
end

zoom(map_px, world_px, fraction) click to toggle source

# File lib/map_project.rb, line 25
def zoom(map_px, world_px, fraction)
  (Math.log(Rational(map_px, world_px) / fraction) / LN2).floor
end