This is an experimental project and has not yet been fully implemented.
If you want to modify atom, here are some other tools that I have tried. Currently, the most recommended is the CLI tool mp4edit in the bento4 project. But because the upstream doesn't merge this PR which added support for colr atom, gama atom, etc, so you have to compile yourself with the commits in that PR to be able to modify colr atom, gama atom, etc. OR you can use the version I compiled, which added support for colr atom, gama atom based on that PR. The executable binary is located at bento4/bin/mp4edit (only target for macOS). For the usage of it, you can check the markdown file located at bento4/commands.md and the help message of mp4edit by running ./mp4edit -h.
I also posted my notes on hacking atoms of Quicktime File Format on my blog, you can check it out if you like.
Modify color primaries, transfer characteristics, matrix coefficients, and gamma value of QuickTime file.
Usage: atom_modifier [OPTIONS] --input-file-path <FILE> --color-primaries <INDEX_VALUE> --transfer-characteristics <INDEX_VALUE> --matrix-coefficients <INDEX_VALUE>
Options:
-i, --input-file-path <FILE>
The path to the input file
-p, --color-primaries <INDEX_VALUE>
Change the "color primaries index" to <INDEX_VALUE>
-t, --transfer-characteristics <INDEX_VALUE>
Change the "transfer characteristics index" to <INDEX_VALUE>
-m, --matrix-coefficients <INDEX_VALUE>
Change the "matrix coefficients index" to <INDEX_VALUE>
-g, --gama-value <GAMA_VALUE>
The gamma value to set. If not present, defaults to -1.0 [default: -1]
-I, --modify-in-place
If passed, modify the input file in-place. Otherwise, create a backup of input file. Defaults to false (create backup)
-h, --help
Print help (see more with '--help')
-V, --version
Print version