import fitz
from rich import inspect
# This creates the Document object doc
doc: fitz.Document = fitz.open("file.pdf")
for page in doc:
    for img in page.get_images():
        xref = img[-2]
        xref_number = img[0]
        pix = fitz.Pixmap(doc, xref)
        bg_color = pix.pixel(pix.width - 1, int(pix.height / 2))
        if bg_color == (12,12,12):
            pix.invert_irect()
            rect = page.get_image_bbox(xref)
            page.insert_image(rect, pixmap=pix, keep_proportion=False)

# doc.save(filename=r"file.new.pdf", clean=True)
# doc.save(filename=r"file.new.pdf", clean=True, garbage=4)
# without deflate_images=1 the file size is 112MB, but now it is just 12MB
doc.save(filename=r"file.new.pdf", clean=True, deflate=4, deflate_images=1, deflate_fonts=1)
doc.close()