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⚡️ Speed up method GlobalGeodetic.TileLatLonBounds by 14% #23

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⚡️ Speed up method GlobalGeodetic.TileLatLonBounds by 14% #23

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39 changes: 23 additions & 16 deletions opendm/tiles/gdal2tiles.py
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Original file line number Diff line number Diff line change
Expand Up @@ -209,7 +209,6 @@ def __init__(self, tileSize=256):
self.initialResolution = 2 * math.pi * 6378137 / self.tileSize
# 156543.03392804062 for tileSize 256 pixels
self.originShift = 2 * math.pi * 6378137 / 2.0
# 20037508.342789244

def LatLonToMeters(self, lat, lon):
"Converts given lat/lon in WGS84 Datum to XY in Spherical Mercator EPSG:3857"
Expand All @@ -223,10 +222,11 @@ def LatLonToMeters(self, lat, lon):
def MetersToLatLon(self, mx, my):
"Converts XY point from Spherical Mercator EPSG:3857 to lat/lon in WGS84 Datum"

lon = (mx / self.originShift) * 180.0
lat = (my / self.originShift) * 180.0

lat = 180 / math.pi * (2 * math.atan(math.exp(lat * math.pi / 180.0)) - math.pi / 2.0)
inv_originShift = 180.0 / self.originShift
lon = mx * inv_originShift
lat = my * inv_originShift
pi = math.pi
lat = 180.0 / pi * (2.0 * math.atan(math.exp(lat * pi / 180.0)) - pi / 2.0)
return lat, lon

def PixelsToMeters(self, px, py, zoom):
Expand Down Expand Up @@ -356,15 +356,17 @@ class GlobalGeodetic(object):

def __init__(self, tmscompatible, tileSize=256):
self.tileSize = tileSize
# Precompute inverse, since division for each call may be expensive if tileSize changes.
inv_tileSize = 1.0 / self.tileSize
if tmscompatible is not None:
# Defaults the resolution factor to 0.703125 (2 tiles @ level 0)
# Adhers to OSGeo TMS spec
# http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification#global-geodetic
self.resFact = 180.0 / self.tileSize
self.resFact = 180.0 * inv_tileSize
else:
# Defaults the resolution factor to 1.40625 (1 tile @ level 0)
# Adheres OpenLayers, MapProxy, etc default resolution for WMTS
self.resFact = 360.0 / self.tileSize
self.resFact = 360.0 * inv_tileSize

def LonLatToPixels(self, lon, lat, zoom):
"Converts lon/lat to pixel coordinates in given zoom of the EPSG:4326 pyramid"
Expand Down Expand Up @@ -403,17 +405,22 @@ def ZoomForPixelSize(self, pixelSize):
return 0 # We don't want to scale up

def TileBounds(self, tx, ty, zoom):
"Returns bounds of the given tile"
res = self.resFact / 2**zoom
return (
tx*self.tileSize*res - 180,
ty*self.tileSize*res - 90,
(tx+1)*self.tileSize*res - 180,
(ty+1)*self.tileSize*res - 90
)
"""Returns bounds of the given tile"""
# Use bitshift for integer powers of two for performance
# This avoids repeated computation of the same value
if isinstance(zoom, int) and 0 <= zoom <= 30:
res = self.resFact / (1 << zoom)
else:
res = self.resFact / 2**zoom
tile_factor = self.tileSize * res
tx0 = tx * tile_factor - 180
ty0 = ty * tile_factor - 90
tx1 = (tx + 1) * tile_factor - 180
ty1 = (ty + 1) * tile_factor - 90
return (tx0, ty0, tx1, ty1)

def TileLatLonBounds(self, tx, ty, zoom):
"Returns bounds of the given tile in the SWNE form"
"""Returns bounds of the given tile in the SWNE form"""
b = self.TileBounds(tx, ty, zoom)
return (b[1], b[0], b[3], b[2])

Expand Down