Image Tiling Utils

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]

Installation:

from pip

pip install tiling

from sources

pip install git+https://github.com/vfdev-5/ImageTilingUtils.git

Examples

For more practical examples, see notebooks