Minimalistic set of image reader agnostic tools to easily iterate over large images
Example 1
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]
Example 2
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]
pip install tiling
pip install git+https://github.com/vfdev-5/ImageTilingUtils.git
For more practical examples, see notebooks