When adding single or multiple images in COLMAP (https://colmap.github.io/), you can modify the image.txt files and add new image information there. This script simplifies the process. When you run it, type the following: python AddImage.py path_to_file_you_want_to_add_images_to (e.g. images.txt) path_to_file_with_image_data (e.g. images_all.txt) path_to_txt_file_with_image_numbers_you_want_to_add