code: def _get_bg_mask_and_cmap(bg_img, black_bg):
      """Get background data for _json_view_data."""
      bg_mask = np.ma.getmaskarray(get_data(bg_img))
      bg_cmap = copy.copy(matplotlib.pyplot.get_cmap("gray"))
      if black_bg:
          bg_cmap.set_bad("black")
      else:
          bg_cmap.set_bad("white")
      return bg_mask, bg_cmap
  
imports: import copy
  import json
  import os
  import warnings
  from base64 import b64encode
  from io import BytesIO
  import matplotlib
  import numpy
  from matplotlib.image import imsave
  from nibabel.affines import apply_affine
  from nilearn.plotting.html_document import HTMLDocument
  from .._utils import fill_doc
  from .._utils.extmath import fast_abs_percentile
  from .._utils.niimg import safe_get_data
  from .._utils.niimg_conversions import check_niimg_3d
  from .._utils.param_validation import check_threshold
  from ..datasets import load_mni152_template
  from ..image import get_data, new_img_like, reorder_img, resample_to_img
  from ..plotting import cm
  from ..plotting.find_cuts import find_xyz_cut_coords
  from ..plotting.img_plotting import load_anat
  from .js_plotting_utils import colorscale, get_html_template
label_desc: Use image node_id 11 for calling a global function with example usage: _get_bg_mask_and_cmap(bg_img, black_bg) and returns: bg_mask,  bg_cmap