InvokeAI/tests/backend/tiles/test_tiles.py

import numpy as np
import pytest

from invokeai.backend.tiles.tiles import (
    calc_tiles_even_split,
    calc_tiles_min_overlap,
    calc_tiles_with_overlap,
    merge_tiles_with_linear_blending,
)
from invokeai.backend.tiles.utils import TBLR, Tile

####################################
# Test calc_tiles_with_overlap(...)
####################################


def test_calc_tiles_with_overlap_single_tile():
    """Test calc_tiles_with_overlap() behavior when a single tile covers the image."""
    tiles = calc_tiles_with_overlap(image_height=512, image_width=1024, tile_height=512, tile_width=1024, overlap=64)

    expected_tiles = [
        Tile(coords=TBLR(top=0, bottom=512, left=0, right=1024), overlap=TBLR(top=0, bottom=0, left=0, right=0))
    ]

    assert tiles == expected_tiles


def test_calc_tiles_with_overlap_evenly_divisible():
    """Test calc_tiles_with_overlap() behavior when the image is evenly covered by multiple tiles."""
    # Parameters chosen so that image is evenly covered by 2 rows, 3 columns of tiles.
    tiles = calc_tiles_with_overlap(image_height=576, image_width=1600, tile_height=320, tile_width=576, overlap=64)

    expected_tiles = [
        # Row 0
        Tile(coords=TBLR(top=0, bottom=320, left=0, right=576), overlap=TBLR(top=0, bottom=64, left=0, right=64)),
        Tile(coords=TBLR(top=0, bottom=320, left=512, right=1088), overlap=TBLR(top=0, bottom=64, left=64, right=64)),
        Tile(coords=TBLR(top=0, bottom=320, left=1024, right=1600), overlap=TBLR(top=0, bottom=64, left=64, right=0)),
        # Row 1
        Tile(coords=TBLR(top=256, bottom=576, left=0, right=576), overlap=TBLR(top=64, bottom=0, left=0, right=64)),
        Tile(coords=TBLR(top=256, bottom=576, left=512, right=1088), overlap=TBLR(top=64, bottom=0, left=64, right=64)),
        Tile(coords=TBLR(top=256, bottom=576, left=1024, right=1600), overlap=TBLR(top=64, bottom=0, left=64, right=0)),
    ]

    assert tiles == expected_tiles


def test_calc_tiles_with_overlap_not_evenly_divisible():
    """Test calc_tiles_with_overlap() behavior when the image requires 'uneven' overlaps to achieve proper coverage."""
    # Parameters chosen so that image is covered by 2 rows and 3 columns of tiles, with uneven overlaps.
    tiles = calc_tiles_with_overlap(image_height=400, image_width=1200, tile_height=256, tile_width=512, overlap=64)

    expected_tiles = [
        # Row 0
        Tile(coords=TBLR(top=0, bottom=256, left=0, right=512), overlap=TBLR(top=0, bottom=112, left=0, right=64)),
        Tile(coords=TBLR(top=0, bottom=256, left=448, right=960), overlap=TBLR(top=0, bottom=112, left=64, right=272)),
        Tile(coords=TBLR(top=0, bottom=256, left=688, right=1200), overlap=TBLR(top=0, bottom=112, left=272, right=0)),
        # Row 1
        Tile(coords=TBLR(top=144, bottom=400, left=0, right=512), overlap=TBLR(top=112, bottom=0, left=0, right=64)),
        Tile(
            coords=TBLR(top=144, bottom=400, left=448, right=960), overlap=TBLR(top=112, bottom=0, left=64, right=272)
        ),
        Tile(
            coords=TBLR(top=144, bottom=400, left=688, right=1200), overlap=TBLR(top=112, bottom=0, left=272, right=0)
        ),
    ]

    assert tiles == expected_tiles


@pytest.mark.parametrize(
    ["image_height", "image_width", "tile_height", "tile_width", "overlap", "raises"],
    [
        (128, 128, 128, 128, 127, False),  # OK
        (128, 128, 128, 128, 0, False),  # OK
        (128, 128, 64, 64, 0, False),  # OK
        (128, 128, 129, 128, 0, True),  # tile_height exceeds image_height.
        (128, 128, 128, 129, 0, True),  # tile_width exceeds image_width.
        (128, 128, 64, 128, 64, True),  # overlap equals tile_height.
        (128, 128, 128, 64, 64, True),  # overlap equals tile_width.
    ],
)
def test_calc_tiles_with_overlap_input_validation(
    image_height: int, image_width: int, tile_height: int, tile_width: int, overlap: int, raises: bool
):
    """Test that calc_tiles_with_overlap() raises an exception if the inputs are invalid."""
    if raises:
        with pytest.raises(AssertionError):
            calc_tiles_with_overlap(image_height, image_width, tile_height, tile_width, overlap)
    else:
        calc_tiles_with_overlap(image_height, image_width, tile_height, tile_width, overlap)


####################################
# Test calc_tiles_min_overlap(...)
####################################


def test_calc_tiles_min_overlap_single_tile():
    """Test calc_tiles_min_overlap() behavior when a single tile covers the image."""
    tiles = calc_tiles_min_overlap(
        image_height=512, image_width=1024, tile_height=512, tile_width=1024, min_overlap=64, round_to_8=False
    )

    expected_tiles = [
        Tile(coords=TBLR(top=0, bottom=512, left=0, right=1024), overlap=TBLR(top=0, bottom=0, left=0, right=0))
    ]

    assert tiles == expected_tiles


def test_calc_tiles_min_overlap_evenly_divisible():
    """Test calc_tiles_min_overlap() behavior when the image is evenly covered by multiple tiles."""
    # Parameters mimic roughly the same output as the original tile generations of the same test name
    tiles = calc_tiles_min_overlap(
        image_height=576, image_width=1600, tile_height=320, tile_width=576, min_overlap=64, round_to_8=False
    )

    expected_tiles = [
        # Row 0
        Tile(coords=TBLR(top=0, bottom=320, left=0, right=576), overlap=TBLR(top=0, bottom=64, left=0, right=64)),
        Tile(coords=TBLR(top=0, bottom=320, left=512, right=1088), overlap=TBLR(top=0, bottom=64, left=64, right=64)),
        Tile(coords=TBLR(top=0, bottom=320, left=1024, right=1600), overlap=TBLR(top=0, bottom=64, left=64, right=0)),
        # Row 1
        Tile(coords=TBLR(top=256, bottom=576, left=0, right=576), overlap=TBLR(top=64, bottom=0, left=0, right=64)),
        Tile(coords=TBLR(top=256, bottom=576, left=512, right=1088), overlap=TBLR(top=64, bottom=0, left=64, right=64)),
        Tile(coords=TBLR(top=256, bottom=576, left=1024, right=1600), overlap=TBLR(top=64, bottom=0, left=64, right=0)),
    ]

    assert tiles == expected_tiles


def test_calc_tiles_min_overlap_not_evenly_divisible():
    """Test calc_tiles_min_overlap() behavior when the image requires 'uneven' overlaps to achieve proper coverage."""
    # Parameters mimic roughly the same output as the original tile generations of the same test name
    tiles = calc_tiles_min_overlap(
        image_height=400, image_width=1200, tile_height=256, tile_width=512, min_overlap=64, round_to_8=False
    )

    expected_tiles = [
        # Row 0
        Tile(coords=TBLR(top=0, bottom=256, left=0, right=512), overlap=TBLR(top=0, bottom=112, left=0, right=168)),
        Tile(coords=TBLR(top=0, bottom=256, left=344, right=856), overlap=TBLR(top=0, bottom=112, left=168, right=168)),
        Tile(coords=TBLR(top=0, bottom=256, left=688, right=1200), overlap=TBLR(top=0, bottom=112, left=168, right=0)),
        # Row 1
        Tile(coords=TBLR(top=144, bottom=400, left=0, right=512), overlap=TBLR(top=112, bottom=0, left=0, right=168)),
        Tile(
            coords=TBLR(top=144, bottom=400, left=448, right=960), overlap=TBLR(top=112, bottom=0, left=168, right=168)
        ),
        Tile(
            coords=TBLR(top=144, bottom=400, left=688, right=1200), overlap=TBLR(top=112, bottom=0, left=168, right=0)
        ),
    ]

    assert tiles == expected_tiles


def test_calc_tiles_min_overlap_difficult_size():
    """Test calc_tiles_min_overlap() behavior when the image is a difficult size to spilt evenly and keep div8."""
    # Parameters are a difficult size for other tile gen routines to calculate
    tiles = calc_tiles_min_overlap(
        image_height=1000, image_width=1000, tile_height=256, tile_width=512, min_overlap=64, round_to_8=False
    )

    expected_tiles = [
        # Row 0
        Tile(coords=TBLR(top=0, bottom=512, left=0, right=512), overlap=TBLR(top=0, bottom=268, left=0, right=268)),
        Tile(coords=TBLR(top=0, bottom=512, left=244, right=756), overlap=TBLR(top=0, bottom=268, left=268, right=268)),
        Tile(coords=TBLR(top=0, bottom=512, left=488, right=1000), overlap=TBLR(top=0, bottom=268, left=268, right=0)),
        # Row 1
        Tile(coords=TBLR(top=244, bottom=756, left=0, right=512), overlap=TBLR(top=268, bottom=268, left=0, right=0)),
        Tile(
            coords=TBLR(top=244, bottom=756, left=244, right=756),
            overlap=TBLR(top=268, bottom=268, left=268, right=268),
        ),
        Tile(
            coords=TBLR(top=244, bottom=756, left=488, right=1000), overlap=TBLR(top=268, bottom=268, left=268, right=0)
        ),
        # Row 2
        Tile(coords=TBLR(top=488, bottom=1000, left=0, right=512), overlap=TBLR(top=268, bottom=0, left=0, right=268)),
        Tile(
            coords=TBLR(top=488, bottom=1000, left=244, right=756), overlap=TBLR(top=268, bottom=0, left=268, right=268)
        ),
        Tile(
            coords=TBLR(top=488, bottom=1000, left=488, right=1000), overlap=TBLR(top=268, bottom=0, left=268, right=0)
        ),
    ]

    assert tiles == expected_tiles


def test_calc_tiles_min_overlap_difficult_size_div8():
    """Test calc_tiles_min_overlap() behavior when the image is a difficult size to spilt evenly and keep div8."""
    # Parameters are a difficult size for other tile gen routines to calculate
    tiles = calc_tiles_min_overlap(
        image_height=1000, image_width=1000, tile_height=256, tile_width=512, min_overlap=64, round_to_8=True
    )

    expected_tiles = [
        # Row 0
        Tile(coords=TBLR(top=0, bottom=512, left=0, right=560), overlap=TBLR(top=0, bottom=272, left=0, right=272)),
        Tile(coords=TBLR(top=0, bottom=512, left=240, right=752), overlap=TBLR(top=0, bottom=272, left=272, right=264)),
        Tile(coords=TBLR(top=0, bottom=512, left=488, right=1000), overlap=TBLR(top=0, bottom=272, left=264, right=0)),
        # Row 1
        Tile(coords=TBLR(top=240, bottom=752, left=0, right=512), overlap=TBLR(top=272, bottom=264, left=0, right=272)),
        Tile(
            coords=TBLR(top=240, bottom=752, left=240, right=752),
            overlap=TBLR(top=272, bottom=264, left=272, right=264),
        ),
        Tile(
            coords=TBLR(top=240, bottom=752, left=488, right=1000), overlap=TBLR(top=272, bottom=264, left=264, right=0)
        ),
        # Row 2
        Tile(coords=TBLR(top=488, bottom=1000, left=0, right=512), overlap=TBLR(top=264, bottom=0, left=0, right=272)),
        Tile(
            coords=TBLR(top=488, bottom=1000, left=240, right=752), overlap=TBLR(top=264, bottom=0, left=272, right=264)
        ),
        Tile(
            coords=TBLR(top=488, bottom=1000, left=488, right=1000), overlap=TBLR(top=264, bottom=0, left=264, right=0)
        ),
    ]

    assert tiles == expected_tiles


@pytest.mark.parametrize(
    ["image_height", "image_width", "tile_height", "tile_width", "min_overlap", "raises"],
    [
        (128, 128, 128, 128, 127, False),  # OK
        (128, 128, 128, 128, 0, False),  # OK
        (128, 128, 64, 64, 0, False),  # OK
        (128, 128, 129, 128, 0, True),  # tile_height exceeds image_height.
        (128, 128, 128, 129, 0, True),  # tile_width exceeds image_width.
        (128, 128, 64, 128, 64, True),  # overlap equals tile_height.
        (128, 128, 128, 64, 64, True),  # overlap equals tile_width.
    ],
)
def test_calc_tiles_min_overlap_input_validation(
    image_height: int,
    image_width: int,
    tile_height: int,
    tile_width: int,
    min_overlap: int,
    raises: bool,
):
    """Test that calc_tiles_min_overlap() raises an exception if the inputs are invalid."""
    if raises:
        with pytest.raises(AssertionError):
            calc_tiles_min_overlap(image_height, image_width, tile_height, tile_width, min_overlap)
    else:
        calc_tiles_min_overlap(image_height, image_width, tile_height, tile_width, min_overlap)


####################################
# Test calc_tiles_even_split(...)
####################################


def test_calc_tiles_even_split_single_tile():
    """Test calc_tiles_even_split() behavior when a single tile covers the image."""
    tiles = calc_tiles_even_split(image_height=512, image_width=1024, num_tiles_x=1, num_tiles_y=1, overlap=0.25)

    expected_tiles = [
        Tile(coords=TBLR(top=0, bottom=512, left=0, right=1024), overlap=TBLR(top=0, bottom=0, left=0, right=0))
    ]

    assert tiles == expected_tiles


def test_calc_tiles_even_split_evenly_divisible():
    """Test calc_tiles_even_split() behavior when the image is evenly covered by multiple tiles."""
    # Parameters mimic roughly the same output as the original tile generations of the same test name
    tiles = calc_tiles_even_split(image_height=576, image_width=1600, num_tiles_x=3, num_tiles_y=2, overlap=0.25)

    expected_tiles = [
        # Row 0
        Tile(coords=TBLR(top=0, bottom=320, left=0, right=624), overlap=TBLR(top=0, bottom=72, left=0, right=136)),
        Tile(coords=TBLR(top=0, bottom=320, left=488, right=1112), overlap=TBLR(top=0, bottom=72, left=136, right=136)),
        Tile(coords=TBLR(top=0, bottom=320, left=976, right=1600), overlap=TBLR(top=0, bottom=72, left=136, right=0)),
        # Row 1
        Tile(coords=TBLR(top=248, bottom=576, left=0, right=624), overlap=TBLR(top=72, bottom=0, left=0, right=136)),
        Tile(
            coords=TBLR(top=248, bottom=576, left=488, right=1112), overlap=TBLR(top=72, bottom=0, left=136, right=136)
        ),
        Tile(coords=TBLR(top=248, bottom=576, left=976, right=1600), overlap=TBLR(top=72, bottom=0, left=136, right=0)),
    ]
    assert tiles == expected_tiles


def test_calc_tiles_even_split_not_evenly_divisible():
    """Test calc_tiles_even_split() behavior when the image requires 'uneven' overlaps to achieve proper coverage."""
    # Parameters mimic roughly the same output as the original tile generations of the same test name
    tiles = calc_tiles_even_split(image_height=400, image_width=1200, num_tiles_x=3, num_tiles_y=2, overlap=0.25)

    expected_tiles = [
        # Row 0
        Tile(coords=TBLR(top=0, bottom=224, left=0, right=464), overlap=TBLR(top=0, bottom=56, left=0, right=104)),
        Tile(coords=TBLR(top=0, bottom=224, left=360, right=824), overlap=TBLR(top=0, bottom=56, left=104, right=104)),
        Tile(coords=TBLR(top=0, bottom=224, left=720, right=1200), overlap=TBLR(top=0, bottom=56, left=104, right=0)),
        # Row 1
        Tile(coords=TBLR(top=168, bottom=400, left=0, right=464), overlap=TBLR(top=56, bottom=0, left=0, right=104)),
        Tile(
            coords=TBLR(top=168, bottom=400, left=360, right=824), overlap=TBLR(top=56, bottom=0, left=104, right=104)
        ),
        Tile(coords=TBLR(top=168, bottom=400, left=720, right=1200), overlap=TBLR(top=56, bottom=0, left=104, right=0)),
    ]

    assert tiles == expected_tiles


def test_calc_tiles_even_split_difficult_size():
    """Test calc_tiles_even_split() behavior when the image is a difficult size to spilt evenly and keep div8."""
    # Parameters are a difficult size for other tile gen routines to calculate
    tiles = calc_tiles_even_split(image_height=1000, image_width=1000, num_tiles_x=2, num_tiles_y=2, overlap=0.25)

    expected_tiles = [
        # Row 0
        Tile(coords=TBLR(top=0, bottom=560, left=0, right=560), overlap=TBLR(top=0, bottom=128, left=0, right=128)),
        Tile(coords=TBLR(top=0, bottom=560, left=432, right=1000), overlap=TBLR(top=0, bottom=128, left=128, right=0)),
        # Row 1
        Tile(coords=TBLR(top=432, bottom=1000, left=0, right=560), overlap=TBLR(top=128, bottom=0, left=0, right=128)),
        Tile(
            coords=TBLR(top=432, bottom=1000, left=432, right=1000), overlap=TBLR(top=128, bottom=0, left=128, right=0)
        ),
    ]

    assert tiles == expected_tiles


@pytest.mark.parametrize(
    ["image_height", "image_width", "num_tiles_x", "num_tiles_y", "overlap", "raises"],
    [
        (128, 128, 1, 1, 0.25, False),  # OK
        (128, 128, 1, 1, 0, False),  # OK
        (128, 128, 2, 1, 0, False),  # OK
        (127, 127, 1, 1, 0, True),  # image size must be dividable by 8
    ],
)
def test_calc_tiles_even_split_input_validation(
    image_height: int, image_width: int, num_tiles_x: int, num_tiles_y: int, overlap: float, raises: bool
):
    """Test that calc_tiles_even_split() raises an exception if the inputs are invalid."""
    if raises:
        with pytest.raises(AssertionError):
            calc_tiles_even_split(image_height, image_width, num_tiles_x, num_tiles_y, overlap)
    else:
        calc_tiles_even_split(image_height, image_width, num_tiles_x, num_tiles_y, overlap)


#############################################
# Test merge_tiles_with_linear_blending(...)
#############################################


@pytest.mark.parametrize("blend_amount", [0, 32])
def test_merge_tiles_with_linear_blending_horizontal(blend_amount: int):
    """Test merge_tiles_with_linear_blending(...) behavior when merging horizontally."""
    # Initialize 2 tiles side-by-side.
    tiles = [
        Tile(coords=TBLR(top=0, bottom=512, left=0, right=512), overlap=TBLR(top=0, bottom=0, left=0, right=64)),
        Tile(coords=TBLR(top=0, bottom=512, left=448, right=960), overlap=TBLR(top=0, bottom=0, left=64, right=0)),
    ]

    dst_image = np.zeros((512, 960, 3), dtype=np.uint8)

    # Prepare tile_images that match tiles. Pixel values are set based on the tile index.
    tile_images = [
        np.zeros((512, 512, 3)) + 64,
        np.zeros((512, 512, 3)) + 128,
    ]

    # Calculate expected output.
    expected_output = np.zeros((512, 960, 3), dtype=np.uint8)
    expected_output[:, : 480 - (blend_amount // 2), :] = 64
    if blend_amount > 0:
        gradient = np.linspace(start=64, stop=128, num=blend_amount, dtype=np.uint8).reshape((1, blend_amount, 1))
        expected_output[:, 480 - (blend_amount // 2) : 480 + (blend_amount // 2), :] = gradient
    expected_output[:, 480 + (blend_amount // 2) :, :] = 128

    merge_tiles_with_linear_blending(
        dst_image=dst_image, tiles=tiles, tile_images=tile_images, blend_amount=blend_amount
    )

    np.testing.assert_array_equal(dst_image, expected_output, strict=True)


@pytest.mark.parametrize("blend_amount", [0, 32])
def test_merge_tiles_with_linear_blending_vertical(blend_amount: int):
    """Test merge_tiles_with_linear_blending(...) behavior when merging vertically."""
    # Initialize 2 tiles stacked vertically.
    tiles = [
        Tile(coords=TBLR(top=0, bottom=512, left=0, right=512), overlap=TBLR(top=0, bottom=64, left=0, right=0)),
        Tile(coords=TBLR(top=448, bottom=960, left=0, right=512), overlap=TBLR(top=64, bottom=0, left=0, right=0)),
    ]

    dst_image = np.zeros((960, 512, 3), dtype=np.uint8)

    # Prepare tile_images that match tiles. Pixel values are set based on the tile index.
    tile_images = [
        np.zeros((512, 512, 3)) + 64,
        np.zeros((512, 512, 3)) + 128,
    ]

    # Calculate expected output.
    expected_output = np.zeros((960, 512, 3), dtype=np.uint8)
    expected_output[: 480 - (blend_amount // 2), :, :] = 64
    if blend_amount > 0:
        gradient = np.linspace(start=64, stop=128, num=blend_amount, dtype=np.uint8).reshape((blend_amount, 1, 1))
        expected_output[480 - (blend_amount // 2) : 480 + (blend_amount // 2), :, :] = gradient
    expected_output[480 + (blend_amount // 2) :, :, :] = 128

    merge_tiles_with_linear_blending(
        dst_image=dst_image, tiles=tiles, tile_images=tile_images, blend_amount=blend_amount
    )

    np.testing.assert_array_equal(dst_image, expected_output, strict=True)


def test_merge_tiles_with_linear_blending_blend_amount_exceeds_vertical_overlap():
    """Test that merge_tiles_with_linear_blending(...) raises an exception if 'blend_amount' exceeds the overlap between
    any vertically adjacent tiles.
    """
    # Initialize 2 tiles stacked vertically.
    tiles = [
        Tile(coords=TBLR(top=0, bottom=512, left=0, right=512), overlap=TBLR(top=0, bottom=64, left=0, right=0)),
        Tile(coords=TBLR(top=448, bottom=960, left=0, right=512), overlap=TBLR(top=64, bottom=0, left=0, right=0)),
    ]

    dst_image = np.zeros((960, 512, 3), dtype=np.uint8)

    # Prepare tile_images that match tiles.
    tile_images = [np.zeros((512, 512, 3)), np.zeros((512, 512, 3))]

    # blend_amount=128 exceeds overlap of 64, so should raise exception.
    with pytest.raises(AssertionError):
        merge_tiles_with_linear_blending(dst_image=dst_image, tiles=tiles, tile_images=tile_images, blend_amount=128)


def test_merge_tiles_with_linear_blending_blend_amount_exceeds_horizontal_overlap():
    """Test that merge_tiles_with_linear_blending(...) raises an exception if 'blend_amount' exceeds the overlap between
    any horizontally adjacent tiles.
    """
    # Initialize 2 tiles side-by-side.
    tiles = [
        Tile(coords=TBLR(top=0, bottom=512, left=0, right=512), overlap=TBLR(top=0, bottom=0, left=0, right=64)),
        Tile(coords=TBLR(top=0, bottom=512, left=448, right=960), overlap=TBLR(top=0, bottom=0, left=64, right=0)),
    ]

    dst_image = np.zeros((512, 960, 3), dtype=np.uint8)

    # Prepare tile_images that match tiles.
    tile_images = [np.zeros((512, 512, 3)), np.zeros((512, 512, 3))]

    # blend_amount=128 exceeds overlap of 64, so should raise exception.
    with pytest.raises(AssertionError):
        merge_tiles_with_linear_blending(dst_image=dst_image, tiles=tiles, tile_images=tile_images, blend_amount=128)


def test_merge_tiles_with_linear_blending_tiles_overflow_dst_image():
    """Test that merge_tiles_with_linear_blending(...) raises an exception if any of the tiles overflows the
    dst_image.
    """
    tiles = [Tile(coords=TBLR(top=0, bottom=512, left=0, right=512), overlap=TBLR(top=0, bottom=0, left=0, right=0))]

    dst_image = np.zeros((256, 512, 3), dtype=np.uint8)

    # Prepare tile_images that match tiles.
    tile_images = [np.zeros((512, 512, 3))]

    with pytest.raises(ValueError):
        merge_tiles_with_linear_blending(dst_image=dst_image, tiles=tiles, tile_images=tile_images, blend_amount=0)


def test_merge_tiles_with_linear_blending_mismatched_list_lengths():
    """Test that merge_tiles_with_linear_blending(...) raises an exception if the lengths of 'tiles' and 'tile_images'
    do not match.
    """
    tiles = [Tile(coords=TBLR(top=0, bottom=512, left=0, right=512), overlap=TBLR(top=0, bottom=0, left=0, right=0))]

    dst_image = np.zeros((256, 512, 3), dtype=np.uint8)

    # tile_images is longer than tiles, so should cause an exception.
    tile_images = [np.zeros((512, 512, 3)), np.zeros((512, 512, 3))]

    with pytest.raises(ValueError):
        merge_tiles_with_linear_blending(dst_image=dst_image, tiles=tiles, tile_images=tile_images, blend_amount=0)