Skip to content

⚡️ Speed up method GlobalMercator.GoogleTile by 56% #19

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

⚡️ Speed up method GlobalMercator.GoogleTile by 56% #19

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 16 additions & 8 deletions opendm/tiles/gdal2tiles.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -204,12 +204,13 @@ class GlobalMercator(object):
"""

def __init__(self, tileSize=256):
"Initialize the TMS Global Mercator pyramid"
"""Initialize the TMS Global Mercator pyramid"""
self.tileSize = tileSize
self.initialResolution = 2 * math.pi * 6378137 / self.tileSize
# 156543.03392804062 for tileSize 256 pixels
self.originShift = 2 * math.pi * 6378137 / 2.0
# 20037508.342789244
# Cache powers of 2 for zoom levels up to a reasonable maximum to optimize repeated calls
self._power_of_2_cache = {}

def LatLonToMeters(self, lat, lon):
"Converts given lat/lon in WGS84 Datum to XY in Spherical Mercator EPSG:3857"
Expand All @@ -223,10 +224,11 @@ 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 @@ -297,10 +299,16 @@ def ZoomForPixelSize(self, pixelSize):
return 0 # We don't want to scale up

def GoogleTile(self, tx, ty, zoom):
"Converts TMS tile coordinates to Google Tile coordinates"
"""Converts TMS tile coordinates to Google Tile coordinates"""

# coordinate origin is moved from bottom-left to top-left corner of the extent
return tx, (2**zoom - 1) - ty
# Keep a small local cache for zoom powers, as this method is called very frequently.
if zoom in self._power_of_2_cache:
max_index = self._power_of_2_cache[zoom]
else:
max_index = 2 ** zoom - 1
self._power_of_2_cache[zoom] = max_index
return tx, max_index - ty

def QuadTree(self, tx, ty, zoom):
"Converts TMS tile coordinates to Microsoft QuadTree"
Expand Down