io

Input/output operations for images and data.

This module handles reading and writing of image files, raw camera data, and parameter files for photoelastic analysis workflows.

io

Functions

split_channels(data)

Splits the data into its respective polarisation channels. Each superpixel is 4x4 pixels, and the channels are arranged in the following order:

R_0 | R_45 | G1_0 | G1_45 R_135 | R_90 | G1_135 | G1_90 G2_0 | G2_45 | B_0 | B_45 G2_135 | G2_90 | B_135 | B_90

Source code in photoelastimetry/io.py

def split_channels(data):
    """
    Splits the data into its respective polarisation channels. Each superpixel
    is 4x4 pixels, and the channels are arranged in the following order:

    R_0 | R_45 | G1_0 | G1_45
    R_135 | R_90 | G1_135 | G1_90
    G2_0 | G2_45 | B_0 | B_45
    G2_135 | G2_90 | B_135 | B_90
    """

    # Reshape the data into a 4D array
    R_0 = data[0::4, 0::4]
    R_45 = data[0::4, 1::4]
    G1_0 = data[0::4, 2::4]
    G1_45 = data[0::4, 3::4]
    R_135 = data[1::4, 0::4]
    R_90 = data[1::4, 1::4]
    G1_135 = data[1::4, 2::4]
    G1_90 = data[1::4, 3::4]
    G2_0 = data[2::4, 0::4]
    G2_45 = data[2::4, 1::4]
    B_0 = data[2::4, 2::4]
    B_45 = data[2::4, 3::4]
    G2_135 = data[3::4, 0::4]
    G2_90 = data[3::4, 1::4]
    B_135 = data[3::4, 2::4]
    B_90 = data[3::4, 3::4]

    # Stack the channels into a 4D array
    I0 = np.stack((R_0, G1_0, G2_0, B_0), axis=-1)
    I90 = np.stack((R_90, G1_90, G2_90, B_90), axis=-1)
    I45 = np.stack((R_45, G1_45, G2_45, B_45), axis=-1)
    I135 = np.stack((R_135, G1_135, G2_135, B_135), axis=-1)

    # data is a 4D array with shape (height, width, colour, polarisation)
    data = np.stack(
        (
            I0,
            I45,
            I90,
            I135,
        ),
        axis=-1,
    )
    return data

save_image(filename, data, metadata={})

Save image data to a file in various formats.

This function saves image data to disk in one of several supported formats, automatically determining the format from the file extension.

Parameters:

Name	Type	Description	Default
filename	str	Path to the output file. The file extension determines the format. Supported extensions: .npy, .raw, .png, .jpg, .jpeg, .tiff, .tif	required
data	ndarray	Image data to save. The data will be cast to the appropriate dtype based on the file format (uint8 for .png/.jpg, uint16 for .tiff, etc.)	required
metadata	dict	Dictionary containing metadata about the image. For .raw format, must contain a "dtype" key specifying the data type to use when saving. Default is empty.	{}

Raises:

Type	Description
ValueError	If the file extension is not one of the supported formats.

Notes

• .npy files preserve the original data type and shape
• .raw files are saved as binary with dtype specified in metadata
• .png and .jpg files convert data to uint8
• .tiff/.tif files convert data to uint16
• matplotlib is used for .png and .jpg formats
• tifffile library is used for .tiff/.tif formats

Examples:

>>> data = np.random.randint(0, 255, (100, 100), dtype=np.uint8)
>>> metadata = {"dtype": "uint8"}
>>> save_image("output.png", data, metadata)

Source code in photoelastimetry/io.py

def save_image(filename, data, metadata={}):
    """
    Save image data to a file in various formats.

    This function saves image data to disk in one of several supported formats,
    automatically determining the format from the file extension.

    Parameters
    ----------
    filename : str
        Path to the output file. The file extension determines the format.
        Supported extensions: .npy, .raw, .png, .jpg, .jpeg, .tiff, .tif
    data : numpy.ndarray
        Image data to save. The data will be cast to the appropriate dtype
        based on the file format (uint8 for .png/.jpg, uint16 for .tiff, etc.)
    metadata : dict
        Dictionary containing metadata about the image. For .raw format, must
        contain a "dtype" key specifying the data type to use when saving. Default is empty.

    Raises
    ------
    ValueError
        If the file extension is not one of the supported formats.

    Notes
    -----
    - .npy files preserve the original data type and shape
    - .raw files are saved as binary with dtype specified in metadata
    - .png and .jpg files convert data to uint8
    - .tiff/.tif files convert data to uint16
    - matplotlib is used for .png and .jpg formats
    - tifffile library is used for .tiff/.tif formats

    Examples
    --------
    >>> data = np.random.randint(0, 255, (100, 100), dtype=np.uint8)
    >>> metadata = {"dtype": "uint8"}
    >>> save_image("output.png", data, metadata)
    """
    output_folder = os.path.dirname(filename)
    if output_folder != "" and not os.path.exists(output_folder):
        os.makedirs(output_folder)

    if filename.endswith(".npy"):
        np.save(filename, data)
    elif filename.endswith(".raw"):
        with open(filename, "wb") as f:
            data.astype(metadata["dtype"]).tofile(f)
    elif filename.endswith(".png"):
        import matplotlib.pyplot as plt

        plt.imsave(filename, data.astype(np.uint8))
    elif filename.endswith(".jpg") or filename.endswith(".jpeg"):
        import matplotlib.pyplot as plt

        plt.imsave(filename, data.astype(np.uint8))
    elif filename.endswith(".tiff") or filename.endswith(".tif"):
        import tifffile

        if data.ndim == 2:
            tifffile.imwrite(filename, data.astype("<f4"))
        elif data.ndim == 3:
            transposed = np.transpose(data, (2, 0, 1))
            tifffile.imwrite(filename, transposed.astype("<f4"), imagej=True, metadata={"axes": "CYX"})
        elif data.ndim == 4:
            # Permute to [4, 3, H, W] so TIFF is interpreted as 4 timepoints of 3-channel images
            transposed = np.transpose(data, (3, 2, 0, 1))
            tifffile.imwrite(filename, transposed.astype("<f4"), imagej=True, metadata={"axes": "TCYX"})
    else:
        raise ValueError(
            f"Unsupported file format for {filename}. Supported formats are .npy, .raw, .png, .jpg, .jpeg, .tiff, .tif"
        )

load_image(filename, metadata=None)

Load image data from a file in various formats.

This function loads image data from disk in one of several supported formats, automatically determining the format from the file extension.

Parameters:

Name	Type	Description	Default
filename	str	Path to the input file. The file extension determines the format. Supported extensions: .npy, .raw, .png, .jpg, .jpeg, .tiff, .tif	required
metadata	dict	Dictionary containing metadata about the image. For .raw format, must contain "width", "height", and "dtype" keys specifying the image dimensions and data type. Default is None.	None

Returns:

Type	Description
ndarray	Loaded image data.

Raises:

Type	Description
ValueError	If the file extension is not one of the supported formats.

Notes

• .npy files preserve the original data type and shape
• .raw files are read as binary with dtype and shape specified in metadata
• .png and .jpg files are loaded as uint8 arrays
• .tiff/.tif files are loaded as uint16 arrays
• matplotlib is used for .png and .jpg formats
• tifffile library is used for .tiff/.tif formats

Examples:

>>> metadata = {"width": 100, "height": 100, "dtype": "uint8"}
>>> data = load_image("input.raw", metadata)

Source code in photoelastimetry/io.py

def load_image(filename, metadata=None):
    """
    Load image data from a file in various formats.

    This function loads image data from disk in one of several supported formats,
    automatically determining the format from the file extension.

    Parameters
    ----------
    filename : str
        Path to the input file. The file extension determines the format.
        Supported extensions: .npy, .raw, .png, .jpg, .jpeg, .tiff, .tif
    metadata : dict, optional
        Dictionary containing metadata about the image. For .raw format, must
        contain "width", "height", and "dtype" keys specifying the image dimensions
        and data type. Default is None.

    Returns
    -------
    numpy.ndarray
        Loaded image data.

    Raises
    ------
    ValueError
        If the file extension is not one of the supported formats.

    Notes
    -----
    - .npy files preserve the original data type and shape
    - .raw files are read as binary with dtype and shape specified in metadata
    - .png and .jpg files are loaded as uint8 arrays
    - .tiff/.tif files are loaded as uint16 arrays
    - matplotlib is used for .png and .jpg formats
    - tifffile library is used for .tiff/.tif formats

    Examples
    --------
    >>> metadata = {"width": 100, "height": 100, "dtype": "uint8"}
    >>> data = load_image("input.raw", metadata)
    """
    if filename.endswith(".npy"):
        data = np.load(filename)
    elif filename.endswith(".raw"):
        with open(filename, "rb") as f:
            data = np.memmap(
                f,
                dtype=metadata["dtype"],
                mode="r",
                offset=0,
                shape=(metadata["height"], metadata["width"]),
            )
            data = np.array(data)
    elif filename.endswith(".png") or filename.endswith(".jpg") or filename.endswith(".jpeg"):
        import matplotlib.pyplot as plt

        data = plt.imread(filename)
    elif filename.endswith(".tiff") or filename.endswith(".tif"):
        import tifffile

        data = tifffile.imread(filename)

        # transpose data to XYC or XYCP format
        if data.ndim == 3:
            data = np.transpose(data, (1, 2, 0))
        elif data.ndim == 4:
            data = np.transpose(data, (2, 3, 1, 0))

    else:
        raise ValueError(
            f"Unsupported file format for {filename}. Supported formats are .npy, .raw, .png, .jpg, .jpeg, .tiff, .tif"
        )

    if metadata is None:
        metadata = {}
        metadata["dtype"] = str(data.dtype)
        metadata["height"] = data.shape[0]
        metadata["width"] = data.shape[1]

    return data, metadata

bin_image(data, binning)

Bin the image by the specified factor.

Parameters:

Name	Type	Description	Default
data	ndarray	Input image data to be binned.	required
binning	int	Binning factor. The image dimensions will be reduced by this factor.	required

Returns:

Type	Description
ndarray	Binned image data.

Source code in photoelastimetry/io.py

def bin_image(data, binning):
    """
    Bin the image by the specified factor.

    Parameters
    ----------
    data : numpy.ndarray
        Input image data to be binned.
    binning : int
        Binning factor. The image dimensions will be reduced by this factor.

    Returns
    -------
    numpy.ndarray
        Binned image data.
    """
    if binning <= 1:
        return data

    # Calculate new shape
    new_height = data.shape[0] // binning
    new_width = data.shape[1] // binning

    # Reshape and bin
    binned_data = (
        data[: new_height * binning, : new_width * binning]
        .reshape(new_height, binning, new_width, binning, *data.shape[2:])
        .mean(axis=(1, 3))
    )

    return binned_data