convolutional_gridding.py 文件源码

def frac_coord(npixel, kernel_oversampling, p):
    """ Compute whole and fractional parts of coordinates, rounded to
    kernel_oversampling-th fraction of pixel size

    The fractional values are rounded to nearest 1/kernel_oversampling pixel value. At
    fractional values greater than (kernel_oversampling-0.5)/kernel_oversampling coordinates are
    rounded to next integer index.

    :param npixel: Number of pixels in total
    :param kernel_oversampling: Fractional values to round to
    :param p: Coordinate in range [-.5,.5[
    """
    assert numpy.array(p >= -0.5).all() and numpy.array(
        p < 0.5).all(), "Cellsize is too large: uv overflows grid uv= %s" % str(p)
    x = npixel // 2 + p * npixel
    flx = numpy.floor(x + 0.5 / kernel_oversampling)
    fracx = numpy.around((x - flx) * kernel_oversampling)
    return flx.astype(int), fracx.astype(int)