Execute this in gimp python fu console to remove black backgrounds from png images while keeping accurate colors

gimp_smart_remove_bg.py

import glob, os
def smart_remove_bg(folder,rem_color="#000000"):
    for filename in glob.glob(folder.replace('"','').strip()):
        out_fname = os.path.join(os.path.dirname(filename),"out-"+os.path.basename(filename))
        out_fname_xcf = os.path.join(os.path.dirname(filename),"xcf-"+os.path.basename(filename)+".xcf")
        image = pdb.file_png_load(filename, filename)
        drawable = pdb.gimp_image_get_active_drawable(image)
        pdb.plug_in_colortoalpha(image, drawable, rem_color)
        layer_copy = pdb.gimp_layer_new_from_drawable(drawable, image)
        pdb.gimp_context_set_sample_criterion(10)
        pdb.gimp_context_set_antialias(0)
        pdb.gimp_context_set_feather(0)
        pdb.gimp_context_set_sample_merged(0)
        pdb.gimp_context_set_sample_transparent(0)
        pdb.gimp_context_set_sample_threshold(255/255)
        pdb.gimp_context_set_foreground(rem_color) 
        pdb.gimp_image_select_color(image, 2, drawable, "#FF0000") # Select whatever left with an insane threeshold
        pdb.gimp_edit_fill(drawable, 0) # And fill it with the color we just removed
        pdb.gimp_image_add_layer(image, layer_copy, 0)
        end_layer = pdb.gimp_image_merge_visible_layers(image, 0)
        pdb.file_png_save(image, end_layer, out_fname, filename, False, 8, False, False, False, False, False)
        pdb.gimp_xcf_save(0, image, end_layer, out_fname_xcf, out_fname_xcf)
        print "Done " + filename


smart_remove_bg( r"file_or_folder" )

Best docx to png here https://cloudconvert.com/docx-to-png