Replace images in a pdf using python

list-code-images.py

import math
import glob
from PIL import Image

for img in glob.glob("images/*.png"):
# for img in ["imageroot-014.png"]:
    with Image.open(img) as im:
        x = math.floor(im.size[0]/2)
        px = im.getpixel((x,-1))
        if px == (12,12,12):
            print(img)

my-story.md

Plan A

1. list images with command: pdfimages -j -png file.pdf img
2. run list-code-images.py to find the dark theme code images
3. invert these image to make them light theme code:

   for f in `cat file.code-images.txt`; do
     convert $f -channel RGB -negate inversed/$f
   done

4. find a way to replace images in a pdf with code (but I gave up here)

Plan B

I end up using PyMuPDF to invert dark theme code images and save them in the same position using replace-images.py.

You will need to install these packages:

pip install fitz PyMuPDF

---

Alhamdulillah, all images replaced. This is an illusion of replacement, because the new images are placed in top of the old images. I think there exists some possible ways to really replace using Document.update_object or Document.update_stream provided by PyMuPDF package.

replace-images.py

import fitz
from os import listdir
# This creates the Document object doc

for file in listdir("./files"):
    doc: fitz.Document = fitz.open(f"./files/{file}")
    for page in doc:
        for img in page.get_images(full=True):
            xref = 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(img)
                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=f"./processed-files/{file}", clean=True, deflate=4, deflate_images=1, deflate_fonts=1)
    doc.close()