Quickstart

Constant stride tiles

Let’s iterate over a large image with overlapping tiles of the same size tiles in pixels. At boundaries we add “no-data” pixels.

Let’s assume the data access is provided with an example function

def read_data(x, y, width, height, out_width=None, out_height=None):
    out_width = width if out_width is None else out_width
    out_height = height if out_height is None else out_height
    img.read(x, y, width, height, out_width, out_height)

Thus, overlapping tiles can be extracted as

from tiling import ConstStrideTiles


tiles = ConstStrideTiles(image_size=(500, 500), tile_size=(256, 256), stride=(100, 100),
                         origin=(-100, -100),
                         scale=1.0,
                         include_nodata=True)

print("Number of tiles: %i" % len(tiles))
for extent, out_size in tiles:
    x, y, width, height = extent
    data = read_data(x, y, width, height,
                     out_width=out_size[0],
                     out_height=out_size[1])
    print("data.shape: {}".format(data.shape))

# Access a tile:
i = len(tiles) // 2
extent, out_size  = tiles[i]

There is also an option generate tiles without “nodata” but while keeping stride constant tile size is reduced at bottom and left boundaries.

Constant size tiles

Let’s iterate over a large image with overlapping tiles of the same size in pixels. In this case we prefer to not going outside the input image and fill tiles with nodata. In this situation, overlapping is not constant.

Let’s assume the data access is provided with an example function

def read_data(x, y, width, height, out_width=None, out_height=None):
    out_width = width if out_width is None else out_width
    out_height = height if out_height is None else out_height
    img.read(x, y, width, height, out_width, out_height)

Thus, overlapping tiles can be extracted as

from tiling import ConstSizeTiles

tiles = ConstSizeTiles(image_size=(500, 500), tile_size=(256, 256), min_overlapping=15, scale=1.0)

print("Number of tiles: %i" % len(tiles))
for extent, out_size in tiles:
    assert out_size[0] == tiles.tile_size[0]
    assert out_size[1] == tiles.tile_size[1]
    x, y, width, height = extent
    data = read_data(x, y, width, height,
                     out_width=out_size[0],
                     out_height=out_size[1])
    print("data.shape: {}".format(data.shape))

# Access a tile:
i = len(tiles) // 2
extent  = tiles[i]