Create an extent for a NOAA radar image using the world file

fetch.py

import io
import PIL.Image
import urllib2
import sys

world_file_url = 'http://radar.weather.gov/ridge/Conus/RadarImg/northeast_radaronly.gfw'
radar_file_url = 'http://radar.weather.gov/ridge/Conus/RadarImg/northeast_radaronly.gif'

# Parse the radar image to find the height and width

radar_file = urllib2.urlopen(radar_file_url)
radar_image_file = io.BytesIO(radar_file.read())
image = PIL.Image.open(radar_image_file)
img_width = image.width
img_height = image.height

# Parse the world file

world_file_contents = urllib2.urlopen(world_file_url).read()
parts = world_file_contents.split('\n')

lng_pixel_width = float(parts[0])
rotation_x = float(parts[1])
rotation_y = float(parts[2])
lat_pixel_width = float(parts[3])
lng_upper_left = float(parts[4])
lat_upper_left = float(parts[5])

# Calculate the extent

west = lng_upper_left
north = lat_upper_left
east = west + (img_width * lng_pixel_width)
south = north + (img_height * lat_pixel_width)

print 'Image Height: %d' % img_height
print 'Image Width: %d' % img_width

print 'West: %s' % west
print 'South: %s' % south
print 'East: %s' % east
print 'North: %s' % north