Copy/download all images in a markdown file to one place, or convert them to base64 (making the markdown doc self-contained).
Notice that some markdown editors (e.g., Typora) might not display huge base64 images properly.
# save images to directory pics that locates in the same directory of where markdown_doc.md locates
python3 main.py "markdown_doc.md" -d "pics"
# convert image paths to base64 images
python3 main.py "markdown_doc.md" -b
# move images, instead of copying
python3 main.py "markdown_doc.md" -m
# modify the original markdown doc instead of creating a new one
python3 main.py "markdown_doc.md" -x