comfyui-ghostwritten-BiRefNet

Ghostwritten Studios — BiRefNet Background Removal

<img width="1920" height="946" alt="image" src="https://github.com/user-attachments/assets/3b0a241c-1784-4c75-b1ca-02ed61c2695e" />

A self-contained ComfyUI custom node for BiRefNet background removal. It does not depend on any other third-party ComfyUI extension, so a ComfyUI update can't silently break the app that relies on it. The only external piece is the model weights, pulled once from Hugging Face and cached locally.

Nodes

| Node | Category | Purpose | |------|----------|---------| | Ghostwritten Remove Background | Ghostwritten Studios | IMAGE → RGBA IMAGE + MASK. Loads the model itself if no loader is connected. | | Ghostwritten BiRefNet Loader | Ghostwritten Studios | (Optional) Load a model once and reuse the handle across multiple nodes. |

Outputs

• rgba_image (IMAGE) — 4-channel RGBA. Feed straight into a Save Image node to get a transparent PNG (ComfyUI's SaveImage writes the alpha channel).
• mask (MASK) — raw foreground matte, 0–1.

Options (Remove Background)

• model_name — BiRefNet (general), BiRefNet_lite (faster), BiRefNet-portrait, BiRefNet HR (1536).
• precision — fp16 (default, CUDA) or fp32.
• mask_blur — feather the matte edge (px).
• mask_offset — grow (+) / shrink (−) the matte (px).
• invert_mask — keep the background instead of the subject.

Model weights

Downloaded automatically on first use via transformers + trust_remote_code=True, cached under ~/.cache/huggingface. Repos:

• ZhengPeng7/BiRefNet · ZhengPeng7/BiRefNet_lite
• ZhengPeng7/BiRefNet-portrait · ZhengPeng7/BiRefNet_HR

Requires timm, einops, kornia (already present in this ComfyUI install).

Minimal API workflow (single node)

{
  "10": { "class_type": "LoadImage", "inputs": { "image": "input.png" } },
  "11": { "class_type": "GhostwrittenRemoveBackground",
          "inputs": { "image": ["10", 0], "model_name": "BiRefNet (general)",
                      "precision": "fp16", "mask_blur": 0, "mask_offset": 0,
                      "invert_mask": false } },
  "12": { "class_type": "SaveImage",
          "inputs": { "filename_prefix": "GhostwrittenStudios_cutout",
                      "images": ["11", 0] } }
}

Restart ComfyUI after installing so the nodes register.