Extensions/comfyui-save-image-watermark
ComfyUI Extension

comfyui-save-image-watermark

Save images with visible watermarks (logo/text), invisible watermarks (LSB steganography), and metadata embedding. Supports PNG/JPEG/WebP with browser download.

By aicuai·Created 8 months ago·Updated 8 months ago· 3
aicuai/comfyui-save-image-watermark
Nodes3
On cloudLocal install
CategoryAICU/Watermark, image
Stars3
Updated8 months ago

Nodes (3)

Extract Hidden Watermark 🔍
AICU/Watermark
Local Save Image
image
Save Image (Watermark) 💧
AICU/Save
Readme

[English] | 日本語

ComfyUI Save Image with Watermark 💧

Custom node for ComfyUI with watermarking capabilities

🎨 This Image Has a Secret

<img src="examples/aicuty_000011.png" width="400" alt="Sample Image"> 
graph TB
    subgraph visible["👁️ Visible Layer"]
        direction LR
        V1["🖼️ Main Image"]
        V2["🅰️ Logo Watermark<br/>(bottom-left)"]
        V3["📝 Text Watermark<br/>(bottom-right)"]
    end

    subgraph invisible["🔒 Invisible Layer - LSB Steganography"]
        direction LR
        I1["Pixel RGB Values"]
        I2["Embedded in<br/>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!

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
<img src="examples/ss-manager-search.png" width="500" alt="ComfyUI Manager Search">

Via Comfy Registry

comfy node registry-install comfyui-save-image-watermark

Manual Installation

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

<img src="examples/ss-workflow-overview.png" width="800" alt="Workflow Overview"> 
flowchart LR
    subgraph input["Input"]
        KS[KSampler] --> VAE[VAEDecode]
        LI[LoadImage<br/>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
<img src="examples/ss-connect-vaedecode.png" width="400" alt="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.

<img src="examples/ss-connect-loadimage.png" width="500" alt="LoadImage Connection">

Step 3: Configure Parameters

Adjust settings using the node's widgets.

<img src="examples/s-parameters.png" width="400" alt="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.

<img src="examples/ss-extract-node.png" width="300" alt="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]
<img src="examples/ss-extract-workflow.png" width="600" alt="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?

graph LR
    subgraph pixel["1 Pixel Structure"]
        R["R: 10000000<br/>(128)"]
        G["G: 10000000<br/>(128)"]
        B["B: 10000000<br/>(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<br/>bit 1"]
    G_LSB --> MSG2["Message<br/>bit 2"]
    B_LSB --> MSG3["Message<br/>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"
<img src="examples/screenshot-photoshop.png" width="600" alt="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

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

Contributing

Issues and Pull Requests are welcome.

Author

AICU Japan K. K.

  • Web: https://aicu.jp
  • GitHub: https://github.com/aicuai