Draw an OSM daily aggregate tile traffic log to an image (proof of concept quality)

draw_osm_day.py

"""
draw_osm_day.py osm_tile_traffic_file.txt output_image.tiff

Write a float32 TIFF representing tile traffic in the OSM aggregate log.

Charlie Loyd, 2023-09-14. Inspired by https://en.osm.town/@pnorman/111062780453196500.

I recommend downloading the .xz compressed files and using xzcat to feed
them to this script. (Doing xz decompression in-script was slow.) E.g.,

$ xzcat tiles-2022-03-15.txt.xz | python draw_osm_day.py - test.tiff

Alpha quality. Gotchas:

- zoom level is hard-coded
- ignores records below zoom level
- does no weighting or scaling of any kind
- etc.

"""

import numpy as np
from skimage import io
from sys import argv

src = argv[1]
if src == '-':
    src = '/dev/stdin'

draw_zl = 10
edge_length = int(2**draw_zl)
dst = np.zeros((edge_length, edge_length), dtype=np.float32)

for line in open(src):
    zxy, count = line.split(" ")
    z, x, y = [int(el) for el in zxy.split("/")]
    
    # z, x, y are original tile coords. We convert those
    # to pixel coords px and py, which are equivalent to
    # what the tile at xyz would be covered by at z=zl.
    # If input z is below zl (would be multiple pixels),
    # we skip it.

    zdiff = z - draw_zl
    if zdiff < 0:
        continue

    px, py = [d >> zdiff for d in (x, y)]

    dst[py, px] += float(count)

# Here you might run dst through, say, log10.

io.imsave(argv[2], dst)