问题
I have noticed that, from Google Maps page, you can get an "embed" link to put inside an iframe and load the map in a browser. (no news here)
The image size can be adjusted to be very large, so I am interested in getting som big images as single .PNGs.
More specifically, I would like to define a rectangular area from a bounding box (upper-right and lower-left coordinates), and get the corresponding image, with an appropriate zoom factor.
But my question is: How can I use Python to get the "pixel content" of this map as an image object?
(My rationale is: if the browser can get and render such image content, then Python should be capable of doing it, too).
EDIT: this is the content of the HTML file that shows my sample map:
<iframe
width="2000"
height="1500"
frameborder="0"
scrolling="yes"
marginheight="0"
marginwidth="0"
src="http://maps.google.com.br/maps?hl=pt-BR&ll=-30.027489,-51.229248&spn=1.783415,2.745209&z=10&output=embed"/>
EDIT: I did as suggested by Ned Batchelder, and read the content of an urllib.urlopen() call using the src address taken from the iframe above. The result was a lot of javascript code, which I think has to do with the Google Maps JavaScript API. So, the question lingers: how could I do some useful stuff from all this stuff in Python in order to get the map image?
EDIT: this link appears to contain some pretty relevant info on how Google Maps tiles their maps: http://www.codeproject.com/KB/scrapbook/googlemap.aspx
also: http://econym.org.uk/gmap/howitworks.htm
回答1:
I thank for all the answers. I ended up solving the problem another way, using Google Maps Static API and some formulas to convert from Coordinate space to Pixel space, so that I can get precise images that "stitch" nicely together.
For anyone interested, here is the code. If it helps someone, please comment!
=============================
import Image, urllib, StringIO
from math import log, exp, tan, atan, pi, ceil
EARTH_RADIUS = 6378137
EQUATOR_CIRCUMFERENCE = 2 * pi * EARTH_RADIUS
INITIAL_RESOLUTION = EQUATOR_CIRCUMFERENCE / 256.0
ORIGIN_SHIFT = EQUATOR_CIRCUMFERENCE / 2.0
def latlontopixels(lat, lon, zoom):
mx = (lon * ORIGIN_SHIFT) / 180.0
my = log(tan((90 + lat) * pi/360.0))/(pi/180.0)
my = (my * ORIGIN_SHIFT) /180.0
res = INITIAL_RESOLUTION / (2**zoom)
px = (mx + ORIGIN_SHIFT) / res
py = (my + ORIGIN_SHIFT) / res
return px, py
def pixelstolatlon(px, py, zoom):
res = INITIAL_RESOLUTION / (2**zoom)
mx = px * res - ORIGIN_SHIFT
my = py * res - ORIGIN_SHIFT
lat = (my / ORIGIN_SHIFT) * 180.0
lat = 180 / pi * (2*atan(exp(lat*pi/180.0)) - pi/2.0)
lon = (mx / ORIGIN_SHIFT) * 180.0
return lat, lon
############################################
# a neighbourhood in Lajeado, Brazil:
upperleft = '-29.44,-52.0'
lowerright = '-29.45,-51.98'
zoom = 18 # be careful not to get too many images!
############################################
ullat, ullon = map(float, upperleft.split(','))
lrlat, lrlon = map(float, lowerright.split(','))
# Set some important parameters
scale = 1
maxsize = 640
# convert all these coordinates to pixels
ulx, uly = latlontopixels(ullat, ullon, zoom)
lrx, lry = latlontopixels(lrlat, lrlon, zoom)
# calculate total pixel dimensions of final image
dx, dy = lrx - ulx, uly - lry
# calculate rows and columns
cols, rows = int(ceil(dx/maxsize)), int(ceil(dy/maxsize))
# calculate pixel dimensions of each small image
bottom = 120
largura = int(ceil(dx/cols))
altura = int(ceil(dy/rows))
alturaplus = altura + bottom
final = Image.new("RGB", (int(dx), int(dy)))
for x in range(cols):
for y in range(rows):
dxn = largura * (0.5 + x)
dyn = altura * (0.5 + y)
latn, lonn = pixelstolatlon(ulx + dxn, uly - dyn - bottom/2, zoom)
position = ','.join((str(latn), str(lonn)))
print x, y, position
urlparams = urllib.urlencode({'center': position,
'zoom': str(zoom),
'size': '%dx%d' % (largura, alturaplus),
'maptype': 'satellite',
'sensor': 'false',
'scale': scale})
url = 'http://maps.google.com/maps/api/staticmap?' + urlparams
f=urllib.urlopen(url)
im=Image.open(StringIO.StringIO(f.read()))
final.paste(im, (int(x*largura), int(y*altura)))
final.show()
回答2:
Rather than trying to use the embed link, you should go directly to the Google API to get images as static graphics. Here's the link to the Google Maps static image API - it looks like you can just pass in the long/lat parameters in the URL just as you do for the normal embeddable one. For example:
http://maps.googleapis.com/maps/api/staticmap?center=-30.027489,-51.229248&size=600x600&zoom=14&sensor=false
gives you an 600x600 street-level overview centered on the co-ordinates you give above, which seems to be Porto Alegre in Brazil. Now you can use urlopen and PIL as Ned suggests:
from cStringIO import StringIO
import Image
import urllib
url = "http://maps.googleapis.com/maps/api/staticmap?center=-30.027489,-51.229248&size=800x800&zoom=14&sensor=false"
buffer = StringIO(urllib.urlopen(url).read())
image = Image.open(buffer)
回答3:
Edit: the code in this answer has been improved and simplified, here: https://stackoverflow.com/a/50536888/5859283
Based on the excellent answer from heltonbiker with changes from BenElgar, below is some updated code for Python 3 and the addition of API key access, hope its useful for somebody:
"""
Stitch together Google Maps images from lat, long coordinates
Based on work by heltonbiker and BenElgar
Changes:
* updated for Python 3
* added Google Maps API key (compliance with T&C, although can set to None)
* handle http request exceptions
"""
import requests
from io import BytesIO
from math import log, exp, tan, atan, pi, ceil
from PIL import Image
import sys
EARTH_RADIUS = 6378137
EQUATOR_CIRCUMFERENCE = 2 * pi * EARTH_RADIUS
INITIAL_RESOLUTION = EQUATOR_CIRCUMFERENCE / 256.0
ORIGIN_SHIFT = EQUATOR_CIRCUMFERENCE / 2.0
GOOGLE_MAPS_API_KEY = None # set to 'your_API_key'
def latlontopixels(lat, lon, zoom):
mx = (lon * ORIGIN_SHIFT) / 180.0
my = log(tan((90 + lat) * pi/360.0))/(pi/180.0)
my = (my * ORIGIN_SHIFT) /180.0
res = INITIAL_RESOLUTION / (2**zoom)
px = (mx + ORIGIN_SHIFT) / res
py = (my + ORIGIN_SHIFT) / res
return px, py
def pixelstolatlon(px, py, zoom):
res = INITIAL_RESOLUTION / (2**zoom)
mx = px * res - ORIGIN_SHIFT
my = py * res - ORIGIN_SHIFT
lat = (my / ORIGIN_SHIFT) * 180.0
lat = 180 / pi * (2*atan(exp(lat*pi/180.0)) - pi/2.0)
lon = (mx / ORIGIN_SHIFT) * 180.0
return lat, lon
def get_maps_image(NW_lat_long, SE_lat_long, zoom=18):
ullat, ullon = NW_lat_long
lrlat, lrlon = SE_lat_long
# Set some important parameters
scale = 1
maxsize = 640
# convert all these coordinates to pixels
ulx, uly = latlontopixels(ullat, ullon, zoom)
lrx, lry = latlontopixels(lrlat, lrlon, zoom)
# calculate total pixel dimensions of final image
dx, dy = lrx - ulx, uly - lry
# calculate rows and columns
cols, rows = int(ceil(dx/maxsize)), int(ceil(dy/maxsize))
# calculate pixel dimensions of each small image
bottom = 120
largura = int(ceil(dx/cols))
altura = int(ceil(dy/rows))
alturaplus = altura + bottom
# assemble the image from stitched
final = Image.new("RGB", (int(dx), int(dy)))
for x in range(cols):
for y in range(rows):
dxn = largura * (0.5 + x)
dyn = altura * (0.5 + y)
latn, lonn = pixelstolatlon(ulx + dxn, uly - dyn - bottom/2, zoom)
position = ','.join((str(latn), str(lonn)))
print(x, y, position)
urlparams = {'center': position,
'zoom': str(zoom),
'size': '%dx%d' % (largura, alturaplus),
'maptype': 'satellite',
'sensor': 'false',
'scale': scale}
if GOOGLE_MAPS_API_KEY is not None:
urlparams['key'] = GOOGLE_MAPS_API_KEY
url = 'http://maps.google.com/maps/api/staticmap'
try:
response = requests.get(url, params=urlparams)
response.raise_for_status()
except requests.exceptions.RequestException as e:
print(e)
sys.exit(1)
im = Image.open(BytesIO(response.content))
final.paste(im, (int(x*largura), int(y*altura)))
return final
############################################
if __name__ == '__main__':
# a neighbourhood in Lajeado, Brazil:
NW_lat_long = (-29.44,-52.0)
SE_lat_long = (-29.45,-51.98)
zoom = 18 # be careful not to get too many images!
result = get_maps_image(NW_lat_long, SE_lat_long, zoom=18)
result.show()
回答4:
This is Daniel Roseman's answer for people that use python 3.x:
- Assuming you got already Google Maps static image API
Python 3.x code:
from io import BytesIO
from PIL import Image
from urllib import request
import matplotlib.pyplot as plt # this is if you want to plot the map using pyplot
url = "http://maps.googleapis.com/maps/api/staticmap?center=-30.027489,-51.229248&size=800x800&zoom=14&sensor=false"
buffer = BytesIO(request.urlopen(url).read())
image = Image.open(buffer)
# Show Using PIL
image.show()
# Or using pyplot
plt.imshow(image)
plt.show()
回答5:
@4Oh4's answer is right, but the maths are way more complicated than they need to be. Conversions between degrees and radians happen way more often than they need to. The Earth's radius is invoked for no reason at all—it cancels in all calculations. An offset is added to the pixel coordinates for no reason at all. The logo cutoff is way bigger than it needs to be. And a few other odds and ends, which have been written in the changes. Here's my version:
#!/usr/bin/env python
"""
Stitch together Google Maps images from lat, long coordinates
Based on work by heltonbiker and BenElgar
Changes:
* updated for Python 3
* added Google Maps API key (compliance with T&C, although can set to None)
* handle http request exceptions
With contributions from Eric Toombs.
Changes:
* Dramatically simplified the maths.
* Set a more reasonable default logo cutoff.
* Added global constants for logo cutoff and max image size.
* Translated a couple presumably Portuguese variable names to English.
"""
import requests
from io import BytesIO
from math import log, exp, tan, atan, ceil
from PIL import Image
import sys
# circumference/radius
tau = 6.283185307179586
# One degree in radians, i.e. in the units the machine uses to store angle,
# which is always radians. For converting to and from degrees. See code for
# usage demonstration.
DEGREE = tau/360
ZOOM_OFFSET = 8
GOOGLE_MAPS_API_KEY = None # set to 'your_API_key'
# Max width or height of a single image grabbed from Google.
MAXSIZE = 640
# For cutting off the logos at the bottom of each of the grabbed images. The
# logo height in pixels is assumed to be less than this amount.
LOGO_CUTOFF = 32
def latlon2pixels(lat, lon, zoom):
mx = lon
my = log(tan((lat + tau/4)/2))
res = 2**(zoom + ZOOM_OFFSET) / tau
px = mx*res
py = my*res
return px, py
def pixels2latlon(px, py, zoom):
res = 2**(zoom + ZOOM_OFFSET) / tau
mx = px/res
my = py/res
lon = mx
lat = 2*atan(exp(my)) - tau/4
return lat, lon
def get_maps_image(NW_lat_long, SE_lat_long, zoom=18):
ullat, ullon = NW_lat_long
lrlat, lrlon = SE_lat_long
# convert all these coordinates to pixels
ulx, uly = latlon2pixels(ullat, ullon, zoom)
lrx, lry = latlon2pixels(lrlat, lrlon, zoom)
# calculate total pixel dimensions of final image
dx, dy = lrx - ulx, uly - lry
# calculate rows and columns
cols, rows = ceil(dx/MAXSIZE), ceil(dy/MAXSIZE)
# calculate pixel dimensions of each small image
width = ceil(dx/cols)
height = ceil(dy/rows)
heightplus = height + LOGO_CUTOFF
# assemble the image from stitched
final = Image.new('RGB', (int(dx), int(dy)))
for x in range(cols):
for y in range(rows):
dxn = width * (0.5 + x)
dyn = height * (0.5 + y)
latn, lonn = pixels2latlon(
ulx + dxn, uly - dyn - LOGO_CUTOFF/2, zoom)
position = ','.join((str(latn/DEGREE), str(lonn/DEGREE)))
print(x, y, position)
urlparams = {
'center': position,
'zoom': str(zoom),
'size': '%dx%d' % (width, heightplus),
'maptype': 'satellite',
'sensor': 'false',
'scale': 1
}
if GOOGLE_MAPS_API_KEY is not None:
urlparams['key'] = GOOGLE_MAPS_API_KEY
url = 'http://maps.google.com/maps/api/staticmap'
try:
response = requests.get(url, params=urlparams)
response.raise_for_status()
except requests.exceptions.RequestException as e:
print(e)
sys.exit(1)
im = Image.open(BytesIO(response.content))
final.paste(im, (int(x*width), int(y*height)))
return final
############################################
if __name__ == '__main__':
# a neighbourhood in Lajeado, Brazil:
NW_lat_long = (-29.44*DEGREE, -52.0*DEGREE)
SE_lat_long = (-29.45*DEGREE, -51.98*DEGREE)
zoom = 18 # be careful not to get too many images!
result = get_maps_image(NW_lat_long, SE_lat_long, zoom=18)
result.show()
回答6:
A more concise Python 2.x compatible method is
from io import BytesIO
import Image
import urllib
url = "http://maps.googleapis.com/maps/api/staticmap?center=52.50058,13.31316&size=800x800&zoom=14"
buffer = BytesIO(urllib.urlopen(url).read())
image = Image.open(buffer)
image.save("map.png")
回答7:
The most simplest way to have the Google static map image captured/saved (as a png):
import requests
img = open('tmp.png','wb')
img.write(requests.get('https://maps.googleapis.com/maps/api/staticmap?center=33.0456,131.3009&zoom=12&size=320x385&key=YOUR_API_KEY').content)
img.close()
回答8:
urllib.urlopen will open a URL, the result will have a .read() method you can use to get the image bytes. cStringIO has a file-like object based on a string in memory. PIL has an Image.open function that opens a file-like thing to give you an image object. Image objects can be asked about their pixel values.
来源：https://stackoverflow.com/questions/7490491/capture-embedded-google-map-image-with-python-without-using-a-browser