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Add intelligent overview selection for tif to pmtiles conversion (#601)

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* load overviews instead of full detail to avoid memory bomb

* fix overview level indexing & use None when no overview for clarity

* tweak nodata value for RGBA
This commit is contained in:
Quentin Chenevier
2025-11-30 14:44:16 +01:00
committed by GitHub
parent 5ef8559b8d
commit 82d53ea0a0
2 changed files with 29 additions and 4 deletions
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27
python/rio-pmtiles/rio_pmtiles/worker.py
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@@ -25,8 +25,9 @@ def init_worker(
warp_opts=None,
creation_opts=None,
exclude_empties=True,
max_zoom=None,
):
global base_kwds, filename, resampling, open_options, warp_options, creation_options, exclude_empty_tiles
global base_kwds, filename, resampling, open_options, warp_options, creation_options, exclude_empty_tiles, max_zoom_level
resampling = Resampling[resampling_method]
base_kwds = profile.copy()
filename = path
@@ -34,6 +35,7 @@ def init_worker(
warp_options = warp_opts.copy() if warp_opts is not None else {}
creation_options = creation_opts.copy() if creation_opts is not None else {}
exclude_empty_tiles = exclude_empties
max_zoom_level = max_zoom
def process_tile(tile):
@@ -54,7 +56,28 @@ def process_tile(tile):
Image bytes corresponding to the tile.
"""
global base_kwds, resampling, filename, open_options, warp_options, creation_options, exclude_empty_tiles
global base_kwds, resampling, filename, open_options, warp_options, creation_options, exclude_empty_tiles, max_zoom_level
# Determine overview level to use
temp_src = rasterio.open(filename)
overviews = temp_src.overviews(1)
temp_src.close()
overview_level = None
if overviews and tile.z < max_zoom_level:
OVERSAMPLING_FACTOR = 4 # oversampling factor to ensure sufficient pixels for resampling operations
target_factor = 2 ** (max_zoom_level - tile.z) / OVERSAMPLING_FACTOR
best_overview = overview_level
best_score = float("inf")
for i_overview, factor in enumerate(overviews):
if factor <= target_factor:
score = abs(factor - target_factor)
if score < best_score:
best_score = score
best_overview = i_overview
overview_level = best_overview
if overview_level is not None:
open_options["OVERVIEW_LEVEL"] = overview_level
with rasterio.open(filename, **open_options) as src: