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maskdownscale

maskdownscale

Module to wrap cython maskdownscale

Functions

get_downscaled_masked_histogram 

get_downscaled_masked_histogram(
    mask_image, num_classes, default_value, ds_factor
)

Calculates a simple histogram for the downscaled mask image Args: mask_image: image to downscale num_classes: number of classes included in image default_value: background value of the image ds_factor: downscale factor

Returns:

  • ndarray –

    Masked histogram

Source code in niceml/utilities/masks/maskdownscale.py 
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def get_downscaled_masked_histogram(
    mask_image: np.ndarray, num_classes: int, default_value: int, ds_factor: int
) -> np.ndarray:
    """
    Calculates a simple histogram for the downscaled mask image
    Args:
        mask_image: image to downscale
        num_classes: number of classes included in image
        default_value: background value of the image
        ds_factor: downscale factor

    Returns:
        Masked histogram
    """
    img_shape = mask_image.shape
    hist_shape = (
        int(img_shape[0] // ds_factor),
        int(img_shape[1] // ds_factor),
        num_classes,
    )
    mask_hist = np.zeros(hist_shape, int)
    mask_image = mask_image.astype(np.uint8)
    try:
        mask_hist = cy_mask_downscale(mask_image, mask_hist, default_value, ds_factor)
    except IndexError as excep:
        max_mask_img = np.max(mask_image[mask_image != default_value])
        raise IndexError(
            f"MaskImage contains {max_mask_img} but "
            f"highest allowed value is: {num_classes - 1}"
        ) from excep
    return mask_hist