Operations on volumetric data

The qim3d library provides a set of methods for different operations on volumes.

qim3d.operations

qim3d.operations.remove_background

remove_background(vol, median_filter_size=2, min_object_radius=3, background='dark', **median_kwargs)

Remove background from a volume using a qim3d filters.

Parameters:

Name	Type	Description	Default
vol	ndarray	The volume to remove background from.	required
median_filter_size	int	The size of the median filter. Defaults to 2.	2
min_object_radius	int	The radius of the structuring element for the tophat filter. Defaults to 3.	3
background	'dark' or 'bright	The background type. Can be 'dark' or 'bright'. Defaults to 'dark'.	'dark'
**median_kwargs	Any	Additional keyword arguments for the Median filter.	{}

Returns:

Name	Type	Description
filtered_vol	ndarray	The volume with background removed.

Example

import qim3d

vol = qim3d.examples.cement_128x128x128
fig1 = qim3d.viz.slices_grid(vol, value_min=0, value_max=255, num_slices=5, display_figure=True)

vol_filtered  = qim3d.operations.remove_background(vol,
                                                      min_object_radius=3,
                                                      background="bright")
fig2 = qim3d.viz.slices_grid(vol_filtered, value_min=0, value_max=255, num_slices=5, display_figure=True)

Source code in qim3d/operations/_common_operations_methods.py

def remove_background(
    vol: np.ndarray,
    median_filter_size: int = 2,
    min_object_radius: int = 3,
    background: str = "dark",
    **median_kwargs,
) -> np.ndarray:
    """
    Remove background from a volume using a qim3d filters.

    Args:
        vol (np.ndarray): The volume to remove background from.
        median_filter_size (int, optional): The size of the median filter. Defaults to 2.
        min_object_radius (int, optional): The radius of the structuring element for the tophat filter. Defaults to 3.
        background ('dark' or 'bright, optional): The background type. Can be 'dark' or 'bright'. Defaults to 'dark'.
        **median_kwargs (Any): Additional keyword arguments for the Median filter.

    Returns:
        filtered_vol (np.ndarray): The volume with background removed.


    Example:
        ```python
        import qim3d

        vol = qim3d.examples.cement_128x128x128
        fig1 = qim3d.viz.slices_grid(vol, value_min=0, value_max=255, num_slices=5, display_figure=True)
        ```
        ![operations-remove_background_before](../../assets/screenshots/operations-remove_background_before.png)

        ```python
        vol_filtered  = qim3d.operations.remove_background(vol,
                                                              min_object_radius=3,
                                                              background="bright")
        fig2 = qim3d.viz.slices_grid(vol_filtered, value_min=0, value_max=255, num_slices=5, display_figure=True)
        ```
        ![operations-remove_background_after](../../assets/screenshots/operations-remove_background_after.png)
    """

    # Create a pipeline with a median filter and a tophat filter
    pipeline = filters.Pipeline(
        filters.Median(size=median_filter_size, **median_kwargs),
        filters.Tophat(radius=min_object_radius, background=background),
    )

    # Apply the pipeline to the volume
    return pipeline(vol)

qim3d.operations.fade_mask

fade_mask(vol, decay_rate=10, ratio=0.5, geometry='spherical', invert=False, axis=0, **kwargs)

Apply edge fading to a volume.

Parameters:

Name	Type	Description	Default
vol	ndarray	The volume to apply edge fading to.	required
decay_rate	float	The decay rate of the fading. Defaults to 10.	10
ratio	float	The ratio of the volume to fade. Defaults to 0.5.	0.5
geometry	spherical or cylindrical	The geometric shape of the fading. Can be 'spherical' or 'cylindrical'. Defaults to 'spherical'.	'spherical'
invert	bool	Flag for inverting the fading. Defaults to False.	False
axis	int	The axis along which to apply the fading. Defaults to 0.	0
**kwargs	Any	Additional keyword arguments for the edge fading.	{}

Returns:

Name	Type	Description
faded_vol	ndarray	The volume with edge fading applied.

Example

import qim3d
vol = qim3d.io.load('heartScan.tif')
qim3d.viz.volumetric(vol)

Image before edge fading has visible artifacts from the support. Which obscures the object of interest.

import qim3d
vol_faded = qim3d.operations.fade_mask(vol, decay_rate=4, ratio=0.45, geometric='cylindrical')
qim3d.viz.volumetrics(vol_faded)

Afterwards the artifacts are faded out, making the object of interest more visible for visualization purposes.

Source code in qim3d/operations/_common_operations_methods.py

def fade_mask(
    vol: np.ndarray,
    decay_rate: float = 10,
    ratio: float = 0.5,
    geometry: str = "spherical",
    invert: bool = False,
    axis: int = 0,
    **kwargs,
) -> np.ndarray:
    """
    Apply edge fading to a volume.

    Args:
        vol (np.ndarray): The volume to apply edge fading to.
        decay_rate (float, optional): The decay rate of the fading. Defaults to 10.
        ratio (float, optional): The ratio of the volume to fade. Defaults to 0.5.
        geometry ('spherical' or 'cylindrical', optional): The geometric shape of the fading. Can be 'spherical' or 'cylindrical'. Defaults to 'spherical'.
        invert (bool, optional): Flag for inverting the fading. Defaults to False.
        axis (int, optional): The axis along which to apply the fading. Defaults to 0.
        **kwargs (Any): Additional keyword arguments for the edge fading.

    Returns:
        faded_vol (np.ndarray): The volume with edge fading applied.

    Example:
        ```python
        import qim3d
        vol = qim3d.io.load('heartScan.tif')
        qim3d.viz.volumetric(vol)
        ```
        Image before edge fading has visible artifacts from the support. Which obscures the object of interest.
        ![operations-edge_fade_before](../../assets/screenshots/operations-edge_fade_before.png)

        ```python
        import qim3d
        vol_faded = qim3d.operations.fade_mask(vol, decay_rate=4, ratio=0.45, geometric='cylindrical')
        qim3d.viz.volumetrics(vol_faded)
        ```
        Afterwards the artifacts are faded out, making the object of interest more visible for visualization purposes.
        ![operations-edge_fade_after](../../assets/screenshots/operations-edge_fade_after.png)

    """
    if 0 > axis or axis >= vol.ndim:
        raise ValueError(
            "Axis must be between 0 and the number of dimensions of the volume"
        )

    # Generate the coordinates of each point in the array
    shape = vol.shape
    z, y, x = np.indices(shape)

    # Store the original maximum value of the volume
    original_max_value = np.max(vol)

    # Calculate the center of the array
    center = np.array([(s - 1) / 2 for s in shape])

    # Calculate the distance of each point from the center
    if geometry == "spherical":
        distance = np.linalg.norm([z - center[0], y - center[1], x - center[2]], axis=0)
    elif geometry == "cylindrical":
        distance_list = np.array([z - center[0], y - center[1], x - center[2]])
        # remove the axis along which the fading is not applied
        distance_list = np.delete(distance_list, axis, axis=0)
        distance = np.linalg.norm(distance_list, axis=0)
    else:
        raise ValueError("Geometry must be 'spherical' or 'cylindrical'")

    # Compute the maximum distance from the center
    max_distance = np.linalg.norm(center)

    # Compute ratio to make synthetic blobs exactly cylindrical
    # target_max_normalized_distance = 1.4 works well to make the blobs cylindrical
    if "target_max_normalized_distance" in kwargs:
        target_max_normalized_distance = kwargs["target_max_normalized_distance"]
        ratio = np.max(distance) / (target_max_normalized_distance * max_distance)

    # Normalize the distances so that they go from 0 at the center to 1 at the farthest point
    normalized_distance = distance / (max_distance * ratio)

    # Apply the decay rate
    faded_distance = normalized_distance**decay_rate

    # Invert the distances to have 1 at the center and 0 at the edges
    fade_array = 1 - faded_distance
    fade_array[fade_array <= 0] = 0

    if invert:
        fade_array = -(fade_array - 1)

    # Apply the fading to the volume
    vol_faded = vol * fade_array

    # Normalize the volume to retain the original maximum value
    vol_normalized = vol_faded * (original_max_value / np.max(vol_faded))

    return vol_normalized

qim3d.operations.overlay_rgb_images

overlay_rgb_images(background, foreground, alpha=0.5, hide_black=True)

Overlay an RGB foreground onto an RGB background using alpha blending.

Parameters:

Name	Type	Description	Default
background	ndarray	The background RGB image.	required
foreground	ndarray	The foreground RGB image (usually masks).	required
alpha	float	The alpha value for blending. Defaults to 0.5.	0.5
hide_black	bool	If True, black pixels will have alpha value 0, so the black won't be visible. Used for segmentation where we don't care about background. Defaults to True.	True

Returns:

Name	Type	Description
composite	ndarray	The composite RGB image with overlaid foreground.

Raises:

Type	Description
ValueError	If input images have different shapes.

Note

• The function performs alpha blending to overlay the foreground onto the background.
• It ensures that the background and foreground have the same first two dimensions (image size matches).
• It can handle greyscale images, values from 0 to 1, raw values which are negative or bigger than 255.
• It calculates the maximum projection of the foreground and blends them onto the background.

Source code in qim3d/operations/_common_operations_methods.py

def overlay_rgb_images(
    background: np.ndarray, foreground: np.ndarray, alpha: float = 0.5, hide_black: bool = True,
) -> np.ndarray:
    """
    Overlay an RGB foreground onto an RGB background using alpha blending.

    Args:
        background (numpy.ndarray): The background RGB image.
        foreground (numpy.ndarray): The foreground RGB image (usually masks).
        alpha (float, optional): The alpha value for blending. Defaults to 0.5.
        hide_black (bool, optional): If True, black pixels will have alpha value 0, so the black won't be visible. Used for segmentation where we don't care about background. Defaults to True.

    Returns:
        composite (numpy.ndarray): The composite RGB image with overlaid foreground.

    Raises:
        ValueError: If input images have different shapes.

    Note:
        - The function performs alpha blending to overlay the foreground onto the background.
        - It ensures that the background and foreground have the same first two dimensions (image size matches).
        - It can handle greyscale images, values from 0 to 1, raw values which are negative or bigger than 255.
        - It calculates the maximum projection of the foreground and blends them onto the background.
    """

    def to_uint8(image:np.ndarray):
        if np.min(image) < 0:
            image = image - np.min(image)

        maxim = np.max(image)
        if maxim > 255:
            image = (image / maxim)*255
        elif maxim <= 1:
            image = image*255

        if image.ndim == 2:
            image = np.repeat(image[..., None], 3, -1)
        elif image.ndim == 3:
            image = image[..., :3] # Ignoring alpha channel
        else:
            raise ValueError(F'Input image can not have higher dimension than 3. Yours have {image.ndim}')

        return image.astype(np.uint8)

    background = to_uint8(background)
    foreground = to_uint8(foreground)

    # Ensure both images have the same shape
    if background.shape != foreground.shape:
        raise ValueError(F"Input images must have the same first two dimensions. But background is of shape {background.shape} and foreground is of shape {foreground.shape}")

    # Perform alpha blending
    foreground_max_projection = np.amax(foreground, axis=2)
    foreground_max_projection = np.stack((foreground_max_projection,) * 3, axis=-1)

    # Normalize if we have something
    if np.max(foreground_max_projection) > 0:
        foreground_max_projection = foreground_max_projection / np.max(
            foreground_max_projection
        )
    # Check alpha validity
    if alpha < 0:
        raise ValueError(F'Alpha has to be positive number. You used {alpha}')
    elif alpha > 1:
        alpha = 1

    # If the pixel is black, its alpha value is set to 0, so it has no effect on the image
    if hide_black:
        alpha = np.full((background.shape[0], background.shape[1],1), alpha)
        alpha[np.apply_along_axis(lambda x: (x == [0,0,0]).all(), axis = 2, arr = foreground)] = 0

    composite = background * (1 - alpha) + foreground * alpha
    composite = np.clip(composite, 0, 255).astype("uint8")

    return composite.astype("uint8")