ComfyUI Prompt Extractor Nodes

Custom nodes for ComfyUI that extract text prompts from PNG image metadata. Recover prompts from any ComfyUI-generated image without needing the original workflow.

✨ Features

• Extract prompts from PNG metadata — Recovers positive and negative prompts from ComfyUI images
• Smart prompt classification — Automatically identifies positive vs negative prompts
• Multiple extraction modes — Longest string, positive only, negative only, or all prompts
• Three node variants — Single image, file path, and batch processing
• Full metadata access — Outputs complete workflow JSON for advanced use cases
• Zero external dependencies — Uses only PIL and standard Python libraries

📦 Installation

Method 1: ComfyUI Manager (Recommended)

Search for "DJZ Prompt Extractor" in ComfyUI Manager and click Install.

Method 2: Manual Installation

Clone this repository into your ComfyUI custom nodes directory:

cd ComfyUI/custom_nodes
git clone https://github.com/MushroomFleet/ComfyUI_PromptExtractor_nodes.git

Restart ComfyUI after installation.

🎛️ Nodes

DJZ Prompt Extractor

The main extraction node. Accepts an image input with an optional file path for metadata access.

Inputs:

Input	Type	Description
image	IMAGE	ComfyUI image tensor
image_path	STRING	Optional: Direct path to PNG file (recommended for full metadata)
extraction_mode	ENUM	How to extract prompts

Outputs:

Output	Type	Description
prompt	STRING	Extracted positive prompt
negative_prompt	STRING	Extracted negative prompt
metadata_json	STRING	Full metadata as JSON

DJZ Prompt Extractor (Path)

Simplified node that takes only a file path. Use when you have the path to a PNG file.

Inputs:

Input	Type	Description
image_path	STRING	Path to PNG file
extraction_mode	ENUM	How to extract prompts

Outputs: Same as main node.

DJZ Prompt Extractor (Batch)

Processes all PNG files in a directory. Useful for bulk prompt extraction.

Inputs:

Input	Type	Description
directory_path	STRING	Path to folder containing PNGs
max_images	INT	Maximum images to process (1-100)
extraction_mode	ENUM	How to extract prompts

Outputs:

Output	Type	Description
prompts_list	STRING	All extracted prompts (separated by ---)
filenames_list	STRING	Corresponding filenames

🔧 Extraction Modes

Mode	Description
longest_string	Returns the longest string found in metadata (default)
positive_only	Attempts to identify and return only the positive prompt
negative_only	Attempts to identify and return only the negative prompt
all_prompts	Returns all found prompts concatenated with | separator

💡 Usage Examples

Basic Prompt Recovery

Connect a Load Image node to the extractor to recover its original prompt:

[Load Image] → [DJZ Prompt Extractor] → [Show Text]
                                      → [CLIP Text Encode]

Re-generate with Extracted Prompt

Use the extracted prompt directly in a new generation:

[Load Image] → [DJZ Prompt Extractor] 
                    ↓ prompt
               [CLIP Text Encode (Positive)]
                    ↓ negative_prompt  
               [CLIP Text Encode (Negative)]
                    ↓
               [KSampler] → [Save Image]

Batch Extract from Output Folder

Extract prompts from all images in your output directory:

[DJZ Prompt Extractor (Batch)]
    directory_path: "ComfyUI/output"
    max_images: 50
         ↓
    [Show Text] — View all extracted prompts

Using File Path for Full Metadata

For complete metadata extraction, provide the file path directly:

[Load Image]
    ↓ image
[DJZ Prompt Extractor]
    image_path: "/path/to/your/image.png"
         ↓
    prompt, negative_prompt, metadata_json

⚠️ Important Notes

PNG Metadata Preservation

ComfyUI embeds workflow and prompt data in PNG tEXt chunks. This metadata is lost when:

• Images are converted to tensors (IMAGE type in ComfyUI)
• Images are re-saved by other applications
• Images are uploaded to social media or image hosts
• Images are converted to JPEG or other formats

For best results: Use the image_path input with the original PNG file path, or use the Path variant node.

Prompt Classification

The node uses two methods to classify prompts as positive or negative:

1. Content analysis — Looks for common negative prompt keywords (ugly, blurry, watermark, deformed, etc.)
2. Workflow tracing — Analyzes node connections to determine if a CLIPTextEncode connects to a sampler's positive or negative input

Classification may not be 100% accurate for unusual workflows or unconventional negative prompts.

🔍 How It Works

1. Read PNG chunks — Parses the PNG file structure to find tEXt and iTXt metadata chunks
2. Extract JSON — ComfyUI stores workflow and prompt data as JSON strings
3. Find CLIPTextEncode nodes — Locates all text encoding nodes in the workflow
4. Extract text inputs — Pulls the text field from each encoder's inputs
5. Classify prompts — Determines positive vs negative based on content and connections
6. Return results — Outputs the classified prompts and full metadata

🌐 Related Projects

This node is the Python/ComfyUI implementation of the prompt extraction logic. A browser-based JSX version is also available:

ComfyUI-Prompt-Extractor-JSX — React component for extracting prompts in web applications

🐛 Troubleshooting

"No prompts extracted" or empty output

• Ensure you're using the original PNG from ComfyUI's output folder
• Check that the file hasn't been re-saved or converted
• Try providing the image_path directly instead of relying on the tensor

Prompts are misclassified

• Use all_prompts mode to see everything found
• Check the metadata_json output for the raw workflow data
• Some custom workflows may not follow standard positive/negative patterns

File not found errors

• Use absolute paths when possible
• Check that the path doesn't contain special characters
• Verify the file exists and is readable

📄 License

MIT License — free for personal and commercial use.

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📚 Citation

Academic Citation

If you use this codebase in your research or project, please cite:

@software{comfyui_prompt_extractor_nodes,
  title = {ComfyUI Prompt Extractor Nodes: Custom nodes for extracting text prompts from PNG metadata},
  author = {Drift Johnson},
  year = {2025},
  url = {https://github.com/MushroomFleet/ComfyUI_PromptExtractor_nodes},
  version = {1.0.0}
}

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