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Fetch and untile tiled Himawari-8 images from the http://himawari8.nict.go.jp PNG endpoint
import requests as req
import sys
from dateutil.parser import parse
from PIL import Image
from StringIO import StringIO
# hi8-fetch.py <date> <zoom level> <output>
# E.g.: hi8-fetch.py 2016-01-13T22:10:00 8 2016-01-13T221000-z8.png
# Fetch Himawari-8 full disks at a given zoom level.
# Valid zoom levels seem to be powers of 2, 1..16, and 20.
#
# To do:
# - Better errors (e.g., catch the "No Image" image).
# - Don't ignore seconds, and/or:
# - option to snap to nearest valid time.
# - Librarify.
# Tile size for this dataset:
width = 550
height = 550
time = parse(sys.argv[1])
scale = int(sys.argv[2])
out = sys.argv[3]
base = 'http://himawari8.nict.go.jp/img/D531106/%sd/550' % (scale)
tiles = [[None] * scale] * scale
def pathfor(t, x, y):
return "%s/%s/%02d/%02d/%02d%02d00_%s_%s.png" \
% (base, t.year, t.month, t.day, t.hour, t.minute, x, y)
def fetch(session, path, retries=1, verbose=False, failure='error'):
# FIXME: this is kinda messy:
if retries < 0:
if failure == 'warning':
raise Warning('Could not download %s (filling with black)')
return np.zeros((width, height, 3))
elif failure == 'silent':
return np.zeros((width, height, 3))
else: # presumed failure == 'error':
raise IOError('Could not download %s')
try:
tiledata = session.get(path).content
tile = Image.open(StringIO(tiledata))
return tile
except:
if verbose:
print('Retrying %s (%s retries left)' % (path, retries))
return fetch(
session,
path,
retries=(retries - 1),
verbose=verbose,
failure=failure
)
sess = req.Session() # so requests will reuse the connection
png = Image.new('RGB', (width*scale, height*scale))
for x in range(scale):
for y in range(scale):
path = pathfor(time, x, y)
tile = fetch(sess, path, retries=4, verbose=True, failure='error')
png.paste(tile, (width*x, height*y, width*(x+1), height*(y+1)))
png.save(out, 'PNG')
joe32097 commented Feb 1, 2016

If I am using py 3.5, how can I get StringIO. Are there any up-to-date-versions?

Any idea how to avoid or catch the "No Image" images? I've got this running every ten minutes and setting my desktop background.

@willwhitney tiles in the "No Image" frames all have the same tiledata, so as long as you're using a scale >= 2 (i.e., at least two frames) you can just check whether any two tiles have the same tiledata. Roughly:

prev_tiledata = ""
for x in range(scale):
  for y in range(scale):
    # ...
    if tiledata == prev_tiledata:
      sys.exit(0)
    prev_tiledata = tiledata
    # ...

I think I also read somewhere that the "No Image" frames happen at specific times, but this works for me.

Nice, that's a solid answer.

Owner
celoyd commented Jun 14, 2016

I also read somewhere that the "No Image" frames happen at specific times

They happen at 02:40 and at 14:40 virtually every day, but they can also happen at other times because of maintenance or random errors, so it’s not enough to hard-code those times.

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