rio-pmtiles python package [#338] (#542)

Add rio-pmtiles command line tool. [#338]

This is derived from the original mapbox/rio-mbtiles implementation, with changes:

* output PMTiles only instead of MBTiles.
* Python 3.7+ only.
* remove --implementation, --image-dump, --append/--overwrite, --covers features.
* bump dependency versions.
* better progress reporting; add pyroaring. 
* update README and license texts.
* rio-pmtiles v0.0.6 on PyPI

python/rio-pmtiles/rio_pmtiles/worker.py

@@ -0,0 +1,138 @@
+"""rio-pmtiles processing worker"""
+
+import logging
+import warnings
+
+from rasterio.enums import Resampling
+from rasterio.io import MemoryFile
+from rasterio.transform import from_bounds as transform_from_bounds
+from rasterio.warp import reproject, transform_bounds
+from rasterio.windows import Window
+from rasterio.windows import from_bounds as window_from_bounds
+import mercantile
+import rasterio
+
+TILES_CRS = "EPSG:3857"
+
+log = logging.getLogger(__name__)
+
+
+def init_worker(
+    path,
+    profile,
+    resampling_method,
+    open_opts=None,
+    warp_opts=None,
+    creation_opts=None,
+    exclude_empties=True,
+):
+    global base_kwds, filename, resampling, open_options, warp_options, creation_options, exclude_empty_tiles
+    resampling = Resampling[resampling_method]
+    base_kwds = profile.copy()
+    filename = path
+    open_options = open_opts.copy() if open_opts is not None else {}
+    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
+
+
+def process_tile(tile):
+    """Process a single PMTiles tile
+
+    Parameters
+    ----------
+    tile : mercantile.Tile
+    warp_options : Mapping
+        GDAL warp options as keyword arguments.
+
+    Returns
+    -------
+
+    tile : mercantile.Tile
+        The input tile.
+    bytes : bytearray
+        Image bytes corresponding to the tile.
+
+    """
+    global base_kwds, resampling, filename, open_options, warp_options, creation_options, exclude_empty_tiles
+
+    with rasterio.open(filename, **open_options) as src:
+
+        bbox = mercantile.xy_bounds(tile)
+
+        kwds = base_kwds.copy()
+        kwds.update(**creation_options)
+        kwds["transform"] = transform_from_bounds(
+            bbox.left, bbox.bottom, bbox.right, bbox.top, kwds["width"], kwds["height"]
+        )
+        src_nodata = kwds.pop("src_nodata", None)
+        dst_nodata = kwds.pop("dst_nodata", None)
+
+        src_alpha = None
+        dst_alpha = None
+        bindexes = None
+
+        if kwds["count"] == 4:
+            bindexes = [1, 2, 3]
+            dst_alpha = 4
+
+            if src.count == 4:
+                src_alpha = 4
+            else:
+                kwds["count"] = 4
+        else:
+            bindexes = list(range(1, kwds["count"] + 1))
+
+        warnings.simplefilter("ignore")
+
+        log.info("Reprojecting tile: tile=%r", tile)
+
+        with MemoryFile() as memfile:
+
+            with memfile.open(**kwds) as tmp:
+
+                # determine window of source raster corresponding to the tile
+                # image, with small buffer at edges
+                try:
+                    west, south, east, north = transform_bounds(
+                        TILES_CRS, src.crs, bbox.left, bbox.bottom, bbox.right, bbox.top
+                    )
+                    tile_window = window_from_bounds(
+                        west, south, east, north, transform=src.transform
+                    )
+                    adjusted_tile_window = Window(
+                        tile_window.col_off - 1,
+                        tile_window.row_off - 1,
+                        tile_window.width + 2,
+                        tile_window.height + 2,
+                    )
+                    tile_window = adjusted_tile_window.round_offsets().round_shape()
+
+                    # if no data in window, skip processing the tile
+                    if (
+                        exclude_empty_tiles
+                        and not src.read_masks(1, window=tile_window).any()
+                    ):
+                        return tile, None
+
+                except ValueError:
+                    log.info(
+                        "Tile %r will not be skipped, even if empty. This is harmless.",
+                        tile,
+                    )
+
+                num_threads = int(warp_options.pop("num_threads", 2))
+
+                reproject(
+                    rasterio.band(src, bindexes),
+                    rasterio.band(tmp, bindexes),
+                    src_nodata=src_nodata,
+                    dst_nodata=dst_nodata,
+                    src_alpha=src_alpha,
+                    dst_alpha=dst_alpha,
+                    num_threads=num_threads,
+                    resampling=resampling,
+                    **warp_options
+                )
+
+            return tile, memfile.read()