chx_correlation.py 文件源码

def _cross_corr(img1, img2=None):
    ''' Compute the cross correlation of one (or two) images.
        Parameters
        ----------
        img1 : np.ndarray
            the image or curve to cross correlate
        img2 : 1d or 2d np.ndarray, optional
            If set, cross correlate img1 against img2.  A shift of img2
            to the right of img1 will lead to a shift of the point of
            highest correlation to the right.
            Default is set to None
    '''
    ndim = img1.ndim

    if img2 is None:
        img2 = img1

    if img1.shape != img2.shape:
        errorstr = "Image shapes don't match. "
        errorstr += "(img1 : {},{}; img2 : {},{})"\
            .format(*img1.shape, *img2.shape)
        raise ValueError(errorstr)

    # need to reverse indices for second image
    # fftconvolve(A,B) = FFT^(-1)(FFT(A)*FFT(B))
    # but need FFT^(-1)(FFT(A(x))*conj(FFT(B(x)))) = FFT^(-1)(A(x)*B(-x))
    reverse_index = [slice(None, None, -1) for i in range(ndim)]
    imgc = fftconvolve(img1, img2[reverse_index], mode='same')

    return imgc