#!/usr/bin/env python
# -*- coding: utf-8 -*-
import math
from pyowm.commons.image import Image
from pyowm.utils.geo import Polygon
[docs]
class Tile:
"""
Wrapper class for an image tile
:param x: horizontal tile number in OWM tile reference system
:type x: int
:param y: vertical tile number in OWM tile reference system
:type y: int
:param zoom: zoom level for the tile
:type zoom: int
:param map_layer: the name of the OWM map layer this tile belongs to
:type map_layer: str
:param image: raw image data
:type image: `pyowm.commons.image.Image instance`
"""
def __init__(self, x, y, zoom, map_layer, image):
assert x >= 0, 'X tile coordinate cannot be negative'
self.x = x
assert y >= 0, 'Y tile coordinate cannot be negative'
self.y = y
assert zoom >= 0, 'Tile zoom level cannot be negative'
self.zoom = zoom
self.map_layer = map_layer
assert isinstance(image, Image), 'The provided image is in invalid format'
self.image = image
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def persist(self, path_to_file):
"""
Saves the tile to disk on a file
:param path_to_file: path to the target file
:type path_to_file: str
:return: `None`
"""
self.image.persist(path_to_file)
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def bounding_polygon(self):
"""
Returns the bounding box polygon for this tile
:return: `pywom.utils.geo.Polygon` instance
"""
lon_left, lat_bottom, lon_right, lat_top = Tile.tile_coords_to_bbox(self.x, self.y, self.zoom)
return Polygon([[[lon_left, lat_top],
[lon_right, lat_top],
[lon_right, lat_bottom],
[lon_left, lat_bottom],
[lon_left, lat_top]]])
[docs]
@classmethod
def tile_coords_for_point(cls, geopoint, zoom):
"""
Returns the coordinates of the tile containing the specified geopoint at the specified zoom level
:param geopoint: the input geopoint instance
:type geopoint: `pywom.utils.geo.Point`
:param zoom: zoom level
:type zoom: int
:return: a tuple (x, y) containing the tile-coordinates
"""
return Tile.geoocoords_to_tile_coords(geopoint.lon, geopoint.lat, zoom)
[docs]
@classmethod
def geoocoords_to_tile_coords(cls, lon, lat, zoom):
"""
Calculates the tile numbers corresponding to the specified geocoordinates at the specified zoom level
Coordinates shall be provided in degrees and using the Mercator Projection (http://en.wikipedia.org/wiki/Mercator_projection)
:param lon: longitude
:type lon: int or float
:param lat: latitude
:type lat: int or float
:param zoom: zoom level
:type zoom: int
:return: a tuple (x, y) containing the tile-coordinates
"""
n = 2.0 ** zoom
x = int((lon + 180.0) / 360.0 * n)
y = int((1.0 - math.log(math.tan(math.radians(lat)) + (1 / math.cos(math.radians(lat)))) / math.pi) / 2.0 * n)
return x, y
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@classmethod
def tile_coords_to_bbox(cls, x, y, zoom):
"""
Calculates the lon/lat estrema of the bounding box corresponding to specific tile coordinates. Output coordinates
are in degrees and in the Mercator Projection (http://en.wikipedia.org/wiki/Mercator_projection)
:param x: the x tile coordinates
:param y: the y tile coordinates
:param zoom: the zoom level
:return: tuple with (lon_left, lat_bottom, lon_right, lat_top)
"""
def tile_to_geocoords(x, y, zoom):
n = 2. ** zoom
lon = x / n * 360. - 180.
lat = math.degrees(math.atan(math.sinh(math.pi * (1 - 2 * y / n))))
return lat, lon
north_west_corner = tile_to_geocoords(x, y, zoom)
south_east_corner = tile_to_geocoords(x+1, y+1, zoom)
return north_west_corner[1], south_east_corner[0], south_east_corner[1], north_west_corner[0]
def __repr__(self):
return "<%s.%s - x=%s, y=%s, zoom=%s, map_layer=%s>" % (
__name__, self.__class__.__name__, self.x, self.y, self.zoom, self.map_layer)
