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c0879bff36
Element drawing module was using flinger for Mercator projection, which is not exactly what is wanted.
131 lines
4.2 KiB
Python
131 lines
4.2 KiB
Python
"""Geo projection."""
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from typing import Optional
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import numpy as np
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from map_machine.geometry.boundary_box import BoundaryBox
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__author__ = "Sergey Vartanov"
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__email__ = "me@enzet.ru"
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def pseudo_mercator(coordinates: np.ndarray) -> np.ndarray:
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"""
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Use spherical pseudo-Mercator projection to convert geo coordinates.
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The result is (x, y), where x is a longitude value, so x is in [-180, 180],
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and y is a stretched latitude and may have any real value:
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(-infinity, +infinity).
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:param coordinates: geo positional in the form of (latitude, longitude)
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:return: position on the plane in the form of (x, y)
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"""
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latitude, longitude = coordinates
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y: float = (
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180.0 / np.pi * np.log(np.tan(np.pi / 4.0 + latitude * np.pi / 360.0))
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)
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return np.array((longitude, y))
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def osm_zoom_level_to_pixels_per_meter(
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zoom_level: float, equator_length: float
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) -> float:
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"""
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Convert OSM zoom level to pixels per meter on Equator.
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See https://wiki.openstreetmap.org/wiki/Zoom_levels
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:param zoom_level: integer number usually not bigger than 20, but this
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function allows any non-negative float value
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:param equator_length: celestial body equator length in meters
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"""
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return 2.0**zoom_level / equator_length * 256.0
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class Flinger:
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"""Interface for flinger that converts coordinates."""
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def __init__(self, size: np.ndarray) -> None:
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self.size: np.ndarray = size
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def fling(self, coordinates: np.ndarray) -> np.ndarray:
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"""Do nothing but return coordinates unchanged."""
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return coordinates
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def get_scale(self, coordinates: Optional[np.ndarray] = None) -> float:
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return 1.0
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class MercatorFlinger(Flinger):
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"""Convert geographical coordinates into (x, y) points on the plane."""
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def __init__(
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self,
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geo_boundaries: BoundaryBox,
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zoom_level: float,
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equator_length: float,
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) -> None:
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"""
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Initialize flinger with geo boundary box and zoom level.
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:param geo_boundaries: minimum and maximum latitude and longitude
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:param zoom_level: zoom level in OpenStreetMap terminology
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:param equator_length: celestial body equator length in meters
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"""
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self.geo_boundaries: BoundaryBox = geo_boundaries
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self.ratio: float = 2.0**zoom_level * 256.0 / 360.0
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size: np.ndarray = self.ratio * (
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pseudo_mercator(self.geo_boundaries.max_())
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- pseudo_mercator(self.geo_boundaries.min_())
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)
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self.pixels_per_meter: float = osm_zoom_level_to_pixels_per_meter(
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zoom_level, equator_length
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)
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size = size.astype(int).astype(float)
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super().__init__(size)
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self.min_ = self.ratio * pseudo_mercator(self.geo_boundaries.min_())
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def fling(self, coordinates: np.ndarray) -> np.ndarray:
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"""
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Convert geo coordinates into (x, y) position points on the plane.
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:param coordinates: geographical coordinates to fling in the form of
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(latitude, longitude)
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"""
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result: np.ndarray = (
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self.ratio * pseudo_mercator(coordinates) - self.min_
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)
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# Invert y axis on coordinate plane.
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result[1] = self.size[1] - result[1]
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return result
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def get_scale(self, coordinates: Optional[np.ndarray] = None) -> float:
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"""
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Return pixels per meter ratio for the given geo coordinates.
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:param coordinates: geographical coordinates in the form of
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(latitude, longitude)
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"""
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if coordinates is None:
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# Get pixels per meter ratio for the center of the boundary box.
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coordinates = self.geo_boundaries.center()
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scale_factor: float = abs(1.0 / np.cos(coordinates[0] / 180.0 * np.pi))
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return self.pixels_per_meter * scale_factor
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class TranslateFlinger(Flinger):
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def __init__(
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self, size: np.ndarray, scale: np.ndarray, offset: np.ndarray
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) -> None:
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super().__init__(size)
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self.scale: np.ndarray = scale
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self.offset: np.ndarray = offset
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def fling(self, coordinates: np.ndarray) -> np.ndarray:
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return self.scale * (coordinates + self.offset)
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