Source code for gammapy.image.utils

# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""Image utility functions"""
from __future__ import absolute_import, division, print_function, unicode_literals
import logging
from multiprocessing import Pool
from functools import partial
import numpy as np
from scipy.signal import fftconvolve
from scipy.ndimage.filters import gaussian_filter
from astropy.convolution import Gaussian2DKernel


__all__ = ["scale_cube"]

log = logging.getLogger(__name__)


def _fftconvolve_wrap(kernel, data):
    # wrap gaussian filter as a special case, because the gain in
    # performance is factor ~100
    if isinstance(kernel, Gaussian2DKernel):
        width = kernel.model.x_stddev.value
        norm = kernel.array.sum()
        return norm * gaussian_filter(data, width)
    else:
        return fftconvolve(data, kernel.array, mode="same")


[docs]def scale_cube(data, kernels, parallel=True): """ Compute scale space cube. Compute scale space cube by convolving the data with a set of kernels and stack the resulting images along the third axis. Parameters ---------- data : `~numpy.ndarray` Input data. kernels: list of `~astropy.convolution.Kernel` List of convolution kernels. parallel : bool Whether to use multiprocessing. Returns ------- cube : `~numpy.ndarray` Array of the shape (len(kernels), data.shape) """ wrap = partial(_fftconvolve_wrap, data=data) if parallel: pool = Pool() result = pool.map(wrap, kernels) pool.close() pool.join() else: result = map(wrap, kernels) return np.dstack(result)