ComfyUI Fast Mosaic Detector

📘 English | 📗 日本語

High-precision & high-speed mosaic detection node for ComfyUI, featuring three modes (FAST / ACCURATE / HYBRID) and adaptive ROI refinement.
The HYBRID mode delivers near-ACCURATE precision at a fraction of the cost (7× faster).

---

🔍 Overview

This node detects mosaic (pixel-block censorship / block-pattern noise) from images or video frames.
It outputs:

• A binary mask (0 or 255)
• Estimated mosaic block size

The detector combines:

• B-mode (FAST) — lightweight, CUDA batch-optimized
• D-mode (ACCURATE) — full histogram + gradient + grid-structure analysis
• HYBRID mode — FAST → ROI extraction → ACCURATE refinement

HYBRID mode typically achieves:

✅ ~85–95% of ACCURATE precision
✅ ~7× faster than ACCURATE
✅ Robust for video sequences

---

Workflow Screenshot

Input Video

https://github.com/user-attachments/assets/17b95590-77cc-435e-8df1-6cf04604c46b

example_input.mp4

Output Video (Image&Mask Blend)

https://github.com/user-attachments/assets/28731ee8-8a11-4971-af86-5be63b44a870

example_output.mp4

---

Example Workflow

You can find the example workflow here:

💾 FastMosaicDetectorExample.json

---

✅ Features

FAST Mode

• ~4 sec for 840[frames]x640x480[pixels] @RTX3090 (210fps)
• May over-detect
• Best for quick estimation

ACCURATE Mode

• ~420 sec for 840[frames]x640x480[pixels] @RTX3090 (0.5fps)
• Best precision
• Full-frame exhaustive scan

HYBRID Mode (Recommended)

• ~40–60 sec for 840[frames]x640x480[pixels] @RTX3090 (14-21fps)
• Near-accurate quality
• Smart ROI refinement
• Recommended for most use cases

---

✅ Inputs & Parameters

Below is the detailed explanation for every parameter in the node.

---

🖼 Image

image: IMAGE

Accepts single images or multi-frame batches.

---

🎛 ACCURATE Mode (D-mode) Parameters

✅ Skin Mask (HSV-based)

| Parameter | Description | |----------|-------------| | hsv_skin_h_low | Minimum hue for skin detection | | hsv_skin_h_high | Maximum hue | | hsv_skin_s_threshold | Minimum saturation |

Helps detect mosaics primarily appearing on skin regions.

---

✅ Gradient Detection

| Parameter | Description | |----------|-------------| | gradient_threshold | Threshold for edge gradient magnitude | | ratio_threshold | Gradient ratio threshold (block pattern strength) | | gradient_band_height | Height of sampling windows | | gradient_band_half_width | Half-width of sampling windows |

Controls how the algorithm identifies block-like structure.

---

✅ Histogram / Grid Structure

| Parameter | Description | |----------|-------------| | histogram_threshold | Required peak ratio of histogram bin | | mosaic_length_min | Minimum block size | | mosaic_length_max | Maximum block size | | intersection_margin | Allowed misalignment |

---

🚀 Execution Mode

mode: FAST | ACCURATE | HYBRID

• FAST → Quick, lower precision
• ACCURATE → Highest precision
• HYBRID → Recommended balance

---

⚙ Backend Selection

processing_backend: AUTO | CPU | TORCH

• AUTO → intelligently selects optimal mode
• CPU → forces CPU
• TORCH → forces PyTorch/CUDA

---

🔧 System Parameters

max_workers

CPU thread count for accurate mode.

Suggested: equal to physical CPU cores.

---

🟦 HYBRID Mode Parameters

fast_recall_boost

Boost recall of FAST detector (0.1–2.0).
Higher → more ROIs but may include noise.

roi_margin_px

Expand ROIs (recommended: 24px)

refine_logic

| Option | Meaning | |--------|---------| | replace | Replace FAST masks with refined results | | union | Merge masks | | intersect | Keep only overlapping |

Default: replace

ROI-related parameters

| Parameter | Description | |----------|-------------| | refine_frame_stride | Interval of refinement | | roi_merge_dilate_px | Unifies ROIs | | roi_max_count | ROI count limit | | min_mask_pixels | Minimum mask size | | frame_cover_threshold | Frame considered over-detected if exceeding ratio |

---

🟩 Adaptive ROI Downscaling

Automatically downscale large ROIs to accelerate refinement.

| Parameter | Description | |----------|-------------| | adaptive_roi_area_ratio | Shrink ROI when > this % of frame | | adaptive_roi_min_side | Small ROIs never downscale | | roi_downscale_large | Downscale rate (0.4–1.0) |

---

🟨 Aspect Ratio Filters

| Parameter | Description | |----------|-------------------------------------------------------| | roi_aspect_ratio_max | Ignore overly elongated ROIs (recommended range: 3-5) | | roi_min_short_side | Ignore too-small ROIs |

Useful for rejecting window frames, bars, non-mosaic patterns.

---

manifest.json

✅ Output

• mask — 0/255 binary mosaic mask
• size — detected mosaic block size

Fully batch-compatible with ComfyUI's image sequences.

---

✅ Recommended Presets

Best Practical

mode = HYBRID
roi_downscale_large = 0.75
roi_aspect_ratio_max = 3.0
fast_recall_boost = 0.9

Highest Precision

mode = ACCURATE

Fast Preview

mode = FAST

---

✅ Notes

• Smaller mosaics require roi_downscale_large = 1.0

• For anime/non-skin content → expand HSV ranges

• If HYBRID misses regions → increase fast_recall_boost

• This node is fully compatible with ComfyUI-VideoHelperSuite for loading video frames and saving processed video outputs. If you plan to use this node with video workflows, installing VideoHelperSuite is strongly recommended.

---

✅ License

MIT

✅ Author

Takahiro Yano
ComfyUI Fast Mosaic Detector