MediaPipe Selfie Segmentation (landscape) — model weights, as ONNX.

- Model: MediaPipe Selfie Segmentation, Copyright The MediaPipe Authors, Apache License 2.0
  (LICENSE-APACHE). https://google.github.io/mediapipe/solutions/selfie_segmentation
- The ONNX file is the conversion made and published by OpenScreen (github.com/getopenscreen/openscreen,
  commit d8bf2d81, public/mediapipe/selfie_segmentation/selfie_segmentation_landscape.onnx; its conversion
  script is MIT, LICENSE-OPENSCREEN-MIT). Copied unchanged.
- Input `input_1` [1, 144, 256, 3] float32 NHWC, RGB 0..1; output `segment_back` [1, 144, 256, 1], sigmoid.
- HyriX (feature 126d) uses it to cut a person out of a clip (Picture › Remove background › Person).
