comfyui-pauseToMask

Pause To Mask (ComfyUI Node)

Pause To Mask is a ComfyUI custom node that pauses workflow execution, exports the current image(s) to disk, lets you edit them externally (for example in Krita), and then resumes execution using the edited image’s alpha channel as a mask.

This node is derived from and inspired by the original ComfyUI‑ImagePreviewPause node by Cordux, and extends it with external‑editor integration and automatic preview refreshing.

Original project: https://github.com/Cordux/ComfyUI-ImagePreviewPause

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✨ Features

• ⏸️ Pauses execution at a specific point in the workflow
• 🖼️ Exports preview images with an alpha channel
• 🎨 One‑click “Send to Krita” (or system image editor fallback)
• 🔄 Auto‑refresh preview while paused
  • Detects file changes using filesystem mtime
  • Updates the ComfyUI preview automatically
• ✅ Resume or cancel execution from the node UI
• 🧠 Mask derived from alpha channel
  • Mask = 1.0 - alpha
  • Optional inversion
  • NEW: Added Sidebar Panel to view current preview

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🧩 Node Behavior

When the node executes:

1. The input image(s) are written to:

   ComfyUI/input/clipspace/

   as RGBA PNG files.

2. The workflow pauses.

3. You can click “Send to Krita” to open the image for editing.

   • If KRITA_PATH is set, Krita is used explicitly.
   • Otherwise, the system default image editor is used.

4. While paused:

   • The node polls file modification time every 2 seconds
   • If the file changes, the preview updates automatically

5. Click:

   • ✅ Continue → workflow resumes, mask is read from alpha
   • ⛔ Cancel → workflow aborts

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🧪 Mask Semantics

• The alpha channel of the edited image is used

• Mask is computed as:

  mask = 1.0 - alpha

• This matches standard ComfyUI masking semantics

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⚙️ Node Inputs

| Input | Type | Description | |------|------|-------------| | images | IMAGE | Image(s) to pause and edit | | auto_refresh | BOOLEAN | Enable / disable preview auto‑refresh while paused |

Auto‑refresh uses a fixed 2‑second interval.
If this feels too aggressive, simply turn it off.

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🧵 Outputs

| Output | Type | |-------|------| | images | IMAGE | | mask | MASK | | mask_inverted | MASK |

🖥️ Krita Integration (Optional)

To force Krita to be used instead of the system default image viewer, set the KRITA_PATH environment variable.

Windows (PowerShell)

setx KRITA_PATH "C:\Program Files\Krita (x64)\bin\krita.exe"

Linux / macOS

export KRITA_PATH=/usr/bin/krita

Restart ComfyUI after setting the variable.

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📁 Files & Structure

pause_to_mask/ ├─ init.py ├─ PauseToMask.py └─ js/ └─ mask_pause.js

• Backend routes are exposed under:

  /api/pause_to_mask/...

• Frontend uses api.fetchApi() for proxy‑safe requests

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🧠 Design Notes

• Auto‑refresh runs only while paused
• Polling stops immediately on Continue or Cancel
• Uses lightweight filesystem mtime checks (no file reads)
• One background thread per paused node, cleaned up safely

This keeps the node responsive and safe for production use.

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🙏 Attribution

This project is based on and inspired by:

ComfyUI‑ImagePreviewPause
by Cordux
https://github.com/Cordux/ComfyUI-ImagePreviewPause

The original project introduced the core idea of previewing and pausing execution directly on a node.

Pause To Mask builds on that foundation by adding:

• external editor workflows (Krita)
• alpha‑based mask extraction
• automatic preview refreshing
• a normalized API and extended control flow

Both projects are released under the MIT License.

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📜 License

MIT License