def blend(arr1, arr2, alpha=0.5):
    """Blend 2 arrays together, mixing with alpha.

        Parameters
        ----------
        arr1:array
                Image 1.
        arr2:array
                Image 2.
        alpha:float
                Higher alpha makes image more like image 1.

        Returns
        -------
        array
                Resulting image.

        """
    return alpha * arr1 + (1.0 - alpha) * arr2