from numpy import array
import pdf2image
import cv2


def open_pdf(pdf, first_page=0, last_page=None):
    first_page += 1
    last_page = None if last_page is None else last_page + 1
    if type(pdf) == str:
        pages = pdf2image.convert_from_path(pdf, first_page=first_page, last_page=last_page)
    elif type(pdf) == bytes:
        pages = pdf2image.convert_from_bytes(pdf, first_page=first_page, last_page=last_page)
    elif type(pdf) == list:
        return pdf
    pages = [array(p) for p in pages]
    return pages


def preprocess_pdf_image(page):
    if len(page.shape) > 2:
        page = cv2.cvtColor(page, cv2.COLOR_BGR2GRAY)
    page = cv2.fastNlMeansDenoising(page, h=3)
    return page