Python function to conveniently resize an image and preserve pixel size. This was found useful to change extent for plt.imshow

resize_img.py

from typing import Any, Tuple
def resize_img(img: np.ndarray, extent_from: Tuple[int, int, int, int], extent_to: Tuple[int, int, int, int], fill_value: Any = 0):
    """
    Resize an image to a new extent, keeping the pixels size.
    The image is cropped if the new extent is smaller than the old one.
    The image is padded with fill_value if the new extent is larger than the old one.

    Parameters:
        img (numpy.ndarray): Input image as a NumPy array.
        extent_from (tuple): Tuple (left, right, top, bottom) representing the current extent of the image.
        extent_to (tuple): Tuple (left, right, top, bottom) representing the desired extent of the image.
        fill_value (Any, optional): The value used for padding. Defaults to 0.

    Returns:
        numpy.ndarray: Resized image as a NumPy array.
    """

    if not isinstance(img, np.ndarray):
        raise ValueError("Input 'img' must be a NumPy array.")
    if len(extent_from) != 4 or len(extent_to) != 4:
        raise ValueError("Both 'extent_from' and 'extent_to' must be tuples of length 4.")

    px_w = (extent_from[1] - extent_from[0]) / img.shape[1]
    px_h = (extent_from[3] - extent_from[2]) / img.shape[0]

    # Calculate the number of pixels to pad/crop.
    # Positive values mean *pad*.
    # Negative values mean *crop*.
    dtop = int((extent_from[2] - extent_to[2]) / px_h)
    dbot = int((extent_to[3] - extent_from[3]) / px_h)
    dleft = int((extent_from[0] - extent_to[0]) / px_w)
    dright = int((extent_to[1] - extent_from[1]) / px_w)

    img = img[
        max(0, -dtop):img.shape[0] - max(0, -dbot),
        max(0, -dleft):img.shape[1] - max(0, -dright)
    ]

    return np.pad(img,
        (
            (max(0, dtop), max(0, dbot)),
            (max(0, dleft), max(0, dright))
        ),
        constant_values=fill_value,
    )