YzPzCode: Skill for Claude Code

Object separation

Separate one subject from the background in a video. Everything runs on the user's computer and nothing is uploaded. The result is the same video with the subject highlighted in green, so the user can see exactly what was separated, plus a mask for every frame saved to disk.

You write and run the Python as you go. The code blocks below are tested; adapt them rather than starting from scratch.

1. Set up in a folder that can be deleted

Needs python 3.10+ and ffmpeg. Install everything into a virtual environment in the project folder, so removing that one folder removes it all:

python3 -m venv .object-separation
.object-separation/bin/pip install torch transformers opencv-python-headless pillow numpy

On Windows use .object-separation\Scripts\pip. With an NVIDIA card on Windows, install the CUDA build of torch from pytorch.org first, because plain pip gives the slower CPU build. Run all the Python below with the venv's python.

2. Scan the computer and pick the model

Run the scan first and tell the user what it found: the device, the model it picked, the download size, and what speed to expect.

Machine	Model	Download
NVIDIA GPU with 12 GB+	facebook/sam2.1-hiera-large	898 MB
NVIDIA GPU under 12 GB, or Apple Silicon	facebook/sam2.1-hiera-base-plus	323 MB
No GPU (CPU only)	facebook/sam2.1-hiera-tiny	156 MB

On a CPU it works but it is slow: about 5 seconds per frame, so a 10 second clip at 30 fps takes around half an hour. It uses under 2 GB of RAM. A GPU is much faster. If the clip is long and there is no GPU, suggest separating only the part the user needs.

# Set these from the user's request. Frame numbers start at 0; the video must be constant frame rate.
VIDEO = "clip.mp4"
START, END = 0, 89              # frames to separate. Click points are picked on the START frame.
PTS = [[480, 270], [100, 60]]   # click points in 960-wide pixels: on the subject first, then on things to leave out
LBL = [1, 0]                    # 1 = this is the subject, 0 = this is NOT the subject