[English] | [日本語](README.ja.md) --- # ComfyUI Save Image with Watermark 💧 Custom node for ComfyUI with watermarking capabilities ## 🎨 This Image Has a Secret Sample Image

```mermaid graph TB subgraph visible["👁️ Visible Layer"] direction LR V1["🖼️ Main Image"] V2["🅰️ Logo Watermark
(bottom-left)"] V3["📝 Text Watermark
(bottom-right)"] end subgraph invisible["🔒 Invisible Layer - LSB Steganography"] direction LR I1["Pixel RGB Values"] I2["Embedded in
Least Significant Bit"] I3["🔐 Hidden Message"] I1 --> I2 --> I3 end IMG["📷 PNG Image File"] IMG --> visible IMG --> invisible style visible fill:#e8f5e9,stroke:#4caf50,stroke-width:2px style invisible fill:#fff8e1,stroke:#ff8f00,stroke-width:2px style I3 fill:#ffebee,stroke:#e53935 ``` > 💡 **Try it yourself!** > ```bash > cd examples > python3 -m venv venv && source venv/bin/activate && pip install Pillow > python lsb_demo.py aicuty_000011.png > # → Extracts "invisible Hello World!" > ``` ## Features ### Image Logo Watermark - **MASK Support**: Accurate alpha blending using LoadImage's MASK output - **Transparent PNG Support**: No black/white bleeding in compositing - **Position, Scale, Opacity**: Fine-grained control ### Text Watermark - **Custom Text**: Configurable font size, color, opacity, position - **Dynamic Text**: Embed seed values etc. from external nodes - **Tile Mode**: Repeat pattern across entire image ### Invisible Watermark (Steganography) - **LSB Embedding**: Hide messages in the least significant bits - **Extraction Node**: Extract embedded hidden messages ### Metadata & Provenance - **Workflow Embedding**: ComfyUI Core compatible workflow saving - **Content Hash**: Generate SHA-256 hash for blockchain provenance - **AICU Metadata**: Watermark info, timestamps, etc. ### Save Options - **output_folder**: Save to ComfyUI output folder - **browser_download**: Download via browser - **both**: Both (default) ## Installation ### Via ComfyUI Manager (Recommended) 1. Launch ComfyUI 2. Click **Manager** button 3. Select **Install Custom Nodes** 4. Search for `watermark` or `aicu` 5. Find **comfyui-save-image-watermark** and click **Install** 6. Restart ComfyUI

### Via Comfy Registry ```bash comfy node registry-install comfyui-save-image-watermark ``` ### Manual Installation ```bash cd ComfyUI/custom_nodes git clone https://github.com/aicuai/comfyui-save-image-watermark.git ``` ### Dependencies This node uses only ComfyUI's standard libraries, no additional dependencies required. - Pillow (bundled with ComfyUI) - NumPy (bundled with ComfyUI) - PyTorch (bundled with ComfyUI) ## Node List ### Save Image (Watermark) 💧 Category: `AICU/Save` Main node for saving images with watermarks. ### Extract Hidden Watermark 🔍 Category: `AICU/Watermark` Node for extracting invisible watermarks (steganography). --- ## How to Use in ComfyUI ### Adding the Node 1. Right-click on canvas → **Add Node** 2. Select **AICU** → **Save** → **Save Image (Watermark) 💧** ### Node Wiring Diagram Workflow Overview

```mermaid flowchart LR subgraph input["Input"] KS[KSampler] --> VAE[VAEDecode] LI[LoadImage
Logo Image] end subgraph main["Save Image (Watermark) 💧"] direction TB I1[/"images (IMAGE)"/] I2[/"watermark_image (IMAGE)"/] I3[/"watermark_image_mask (MASK)"/] I4[/"dynamic_text (STRING)"/] O1[\"image (IMAGE)"\] O2[\"filename (STRING)"\] O3[\"content_hash (STRING)"\] end subgraph output["Output"] PREVIEW[PreviewImage] NEXT[Next Node...] end VAE -->|IMAGE| I1 LI -->|IMAGE| I2 LI -->|MASK| I3 O1 --> PREVIEW O1 --> NEXT ``` ### Basic Connections #### Step 1: Connect Source Image Connect your generated image to the `images` pin. ``` [KSampler] → [VAEDecode] → images ``` VAEDecode Connection

#### Step 2: Connect Logo Image (Optional) To add a logo watermark, connect two wires from LoadImage node. ``` [LoadImage] ├─ IMAGE → watermark_image └─ MASK → watermark_image_mask ← Important! Alpha info ``` > ⚠️ **Don't forget MASK!** Without MASK, transparent areas will appear black. LoadImage Connection

#### Step 3: Configure Parameters Adjust settings using the node's widgets. Parameter Settings

### Input Pins (Left Side) | Pin Name | Type | Required | Description | |----------|------|----------|-------------| | **images** | IMAGE | ✅ | Source image. Connect VAEDecode output | | **watermark_image** | IMAGE | - | Logo image. Connect LoadImage IMAGE output | | **watermark_image_mask** | MASK | - | Logo alpha. Connect LoadImage MASK output | | **dynamic_text** | STRING | - | Dynamic text. Can connect seed values etc. | ### Output Pins (Right Side) | Pin Name | Type | Description | |----------|------|-------------| | **image** | IMAGE | Processed image. Can connect to subsequent nodes | | **filename** | STRING | Saved filename | | **content_hash** | STRING | SHA-256 hash (for provenance) | --- ### Parameter Details #### Basic Settings | Parameter | Type | Default | Description | |-----------|------|---------|-------------| | `filename_prefix` | STRING | "aicuty" | Filename prefix. Numbered like `aicuty_00001_.png` | | `file_format` | ENUM | PNG | Save format. **PNG recommended** (preserves LSB) | | `save_to` | ENUM | both | Destination. `output_folder` / `browser_download` / `both` | #### Image Logo Watermark | Parameter | Type | Default | Description | |-----------|------|---------|-------------| | `watermark_image_position` | ENUM | bottom_left | Logo position | | `watermark_image_scale` | FLOAT | 0.15 | Logo ratio to image width (1%-100%) | | `watermark_image_opacity` | FLOAT | 1.0 | Opacity (0.0=transparent, 1.0=opaque) | #### Text Watermark | Parameter | Type | Default | Description | |-----------|------|---------|-------------| | `watermark_text` | STRING | "© AICU" | Watermark text | | `watermark_text_enabled` | BOOL | True | Enable/disable text watermark | | `watermark_text_position` | ENUM | bottom_right | Text position | | `watermark_text_opacity` | FLOAT | 0.9 | Opacity | | `watermark_text_size` | INT | 24 | Font size (8-128px) | | `watermark_text_color` | STRING | #FFFFFF | Text color (HEX format) | #### Invisible Watermark (LSB) | Parameter | Type | Default | Description | |-----------|------|---------|-------------| | `invisible_watermark` | STRING | "" | Secret message to embed | | `invisible_watermark_enabled` | BOOL | False | Enable/disable invisible watermark | > ⚠️ **Note**: Invisible watermarks are preserved **only in PNG format**. JPEG/WebP will destroy them. #### Metadata | Parameter | Type | Default | Description | |-----------|------|---------|-------------| | `embed_workflow` | BOOL | True | Embed ComfyUI workflow | | `embed_metadata` | BOOL | True | Embed AICU metadata | | `metadata_json` | STRING | "{}" | Custom JSON metadata | #### Quality Settings | Parameter | Type | Default | Description | |-----------|------|---------|-------------| | `jpeg_quality` | INT | 95 | JPEG quality (1-100) | | `webp_quality` | INT | 90 | WebP quality (1-100) | --- ### Position Options ``` ┌────────────────────────────────────────┐ │ top_left top_right │ │ ◆ ◆ │ │ │ │ center │ │ ◆ │ │ │ │ ◆ ◆ │ │ bottom_left bottom_right │ └────────────────────────────────────────┘ tile: Repeat pattern across entire image ``` --- ### Extract Hidden Watermark 🔍 Node Node for extracting LSB steganography messages. Extract Hidden Watermark Node

#### Input Pins | Pin Name | Type | Description | |----------|------|-------------| | **image** | IMAGE | Image to extract from | #### Parameters | Parameter | Type | Default | Description | |-----------|------|---------|-------------| | `max_length` | INT | 1000 | Maximum characters to read | #### Output Pins | Pin Name | Type | Description | |----------|------|-------------| | **hidden_message** | STRING | Extracted message | #### Usage Example ``` [LoadImage] ──IMAGE──→ [Extract Hidden Watermark 🔍] ──STRING──→ [ShowText] ``` Extraction Workflow Example

--- ## Processing Order ``` 1. Image Logo Watermark (bottom layer) └─ Blend only in MASK areas with opacity 2. Text Watermark (above logo) └─ Combined with dynamic text 3. Invisible Watermark (last) └─ LSB Steganography 4. File Save ``` --- ## Technical Specifications ### Image Logo Blending - MASK=0: Fully transparent (no blending) - MASK=255: Blend with opacity value - Formula: `result = base * (1 - mask * opacity) + logo * (mask * opacity)` ### Invisible Watermark (LSB) This implementation uses **simple LSB (Least Significant Bit) method**. #### What is LSB? ```mermaid graph LR subgraph pixel["1 Pixel Structure"] R["R: 10000000
(128)"] G["G: 10000000
(128)"] B["B: 10000000
(128)"] end subgraph lsb["Least Significant Bit (LSB)"] R --> R_LSB["0"] G --> G_LSB["0"] B --> B_LSB["0"] end R_LSB --> MSG["Message
bit 1"] G_LSB --> MSG2["Message
bit 2"] B_LSB --> MSG3["Message
bit 3"] style R fill:#ffcdd2 style G fill:#c8e6c9 style B fill:#bbdefb ``` ``` Example: Embedding "H" (ASCII 72 = 01001000) Original Pixel After Embedding Change ───────────────────────────────────────────── Pixel[0] R: 128 (10000000) → 128 (1000000[0]) LSB=0 ✓ G: 128 (10000000) → 129 (1000000[1]) LSB=1 ← Changed! B: 128 (10000000) → 128 (1000000[0]) LSB=0 ✓ The 128 → 129 change is invisible to human eyes! ``` > 💡 **Try it**: `python examples/lsb_demo.py --create-gray` #### Algorithm **Embedding Process:** 1. Convert message to UTF-8 byte sequence 2. Add termination marker (4 NULL bytes `\x00\x00\x00\x00`) 3. Split each byte into 8 bits 4. Overwrite LSB of each pixel's R, G, B values sequentially 5. Alpha channel (transparency) is not modified **Extraction Process:** 1. Get LSB from each pixel's R, G, B values sequentially 2. Collect 8 bits to reconstruct bytes 3. Stop when termination marker (4 consecutive NULL bytes) is detected 4. Decode byte sequence as UTF-8 to recover message #### Specifications - Maximum capacity: `(width × height × 3) / 8` bytes - Termination marker: 4 bytes (`\x00\x00\x00\x00`) - Encoding: UTF-8 #### ⚠️ Important Limitations **This method is vulnerable to image processing. The following operations will destroy data:** | Operation | Effect | |-----------|--------| | JPEG save | ❌ Completely destroyed (lossy compression changes LSB) | | WebP save (lossy) | ❌ Completely destroyed | | Resize | ❌ Completely destroyed (pixel interpolation changes LSB) | | Crop | ❌ Completely destroyed (pixel positions shift) | | Rotation | ❌ Completely destroyed | | Color adjustment | ❌ Completely destroyed | | PNG re-save | ✅ Preserved (lossless compression) | **Recommendations:** - Use **PNG format only** when using invisible watermarks - Do not process the image before extraction - For robustness, wait for future DCT/DWT implementation #### Security Notice - Current implementation has **no encryption** - Embedding position is **fixed pattern** (sequential from top-left) - Third parties can extract using the same algorithm - Not suitable for embedding confidential information ### Content Hash - Algorithm: SHA-256 - Input: Image byte sequence encoded as PNG - Output: 64-character hexadecimal string --- ## Experiment: Does LSB Survive Photoshop Editing? LSB steganography is said to be "vulnerable to image processing", but what actually happens when editing with Photoshop? ### Test Environment - Adobe Photoshop 2026 - macOS - Source: 128x128 gray image (with "Hello LSB!" embedded via LSB) ### Procedure 1. Open LSB-embedded image in Photoshop 2. Add text using text tool 3. Save with **"Quick Export as PNG"** Photoshop Export Steps

### Results ``` 【Pixel Analysis】 First changed pixel: Row 13, Column 43 (text area only) Changed pixels: 9.2% (text area only) 【LSB Message Area】 Location: Row 0, Columns 0-37 (first 38 pixels) Status: Completely intact ✅ 【Extraction Test】 Original: 'Hello LSB!' After Photoshop: 'Hello LSB!' 🎉 Decoding successful! ``` ### Why It Survived | Factor | Explanation | |--------|-------------| | **Export method** | "Quick Export as PNG" has minimal optimization | | **Color profile** | No conversion (embedded profile maintained) | | **Edit location** | Text in center, LSB data in top-left → no overlap | | **File format** | Saved as PNG (lossless) | ### Survival Conditions ```mermaid flowchart TD A[Edit in Photoshop] --> B{Color profile conversion?} B -->|Yes| X[❌ Destroyed] B -->|No| C{Save format?} C -->|JPEG/WebP| X C -->|PNG| D{Edit location?} D -->|Top-left edited| X D -->|Center/bottom-right| E[✅ Survives] ``` ### Conclusion > LSB steganography is more durable than expected... but don't trust it It's not simply "PNG re-save is OK" - **where you edit** matters. However, this is not a security feature - use only as an **experimental watermark**. --- ## Future Plans ### Text Decoration - Custom font support - Stroke (outline) - Drop shadow - Text rotation - Background box ### Advanced Steganography - DCT (Discrete Cosine Transform) method - DWT (Discrete Wavelet Transform) method - Position shuffling with encryption key - Error correction codes ### Other - Logo rotation & blend modes - C2PA signature support ## License Apache License 2.0 ## Related Projects - [ComfyUI Master Guide](https://j.aicu.ai/comfysb) - [comfyui-save-image-local](https://github.com/yhayano-ponotech/comfyui-save-image-local) - Original save node - [C2PA](https://c2pa.org/) - Content Credentials standard ## Contributing Issues and Pull Requests are welcome. ## Author AICU Japan K. K. - Web: https://aicu.jp - GitHub: https://github.com/aicuai

Extract Hidden Watermark 🔍

Inputs (2)

Outputs (1)