What It Does
SaveImage is the final node in most ComfyUI workflows. It accepts an IMAGE tensor, writes it to PNG format in the configured output directory, and embeds two metadata chunks in the PNG file: the "workflow" chunk (the full node graph as JSON) and the "prompt" chunk (the flattened execution parameters).
This makes SaveImage the most provenance-rich built-in output option. The embedded workflow JSON contains every node, connection, and parameter value from the generation session. Any downstream tool that reads PNG metadata—including Numonic—can reconstruct the exact generation state from a SaveImage output.
The key limitation is relational: SaveImage produces isolated files with no awareness of session, project, or lineage across multiple generations. Each PNG is an island.
Inputs
imagesIMAGEThe rendered image tensor to save.
filename_prefixSTRINGoptionalPrefix for the output filename.
What Numonic Captures
- Full workflow JSON (node graph, connections, per-node parameters)
- Prompt JSON (flattened execution parameters)
- Model name (as referenced in the workflow)
- Sampler settings (steps, CFG, sampler name, scheduler)
- Seed value (resolved, even when randomization was used)
- Image dimensions (width, height)
- Filename and output path
Known Gaps
- Model file checksums — filename recorded, not a hash
- Input image provenance — img2img sources not referenced in output
- Generation timing — no timestamp of when the image was created
- Session context — no relationship between outputs from the same run
Related Nodes
Capture ComfyUI metadata automatically
Numonic extracts workflow metadata from every ComfyUI generation — models, samplers, seeds, prompts, and custom nodes. Track provenance, maintain compliance, and never lose a workflow.