managing-thumbnails

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Manages thumbnail and preview images for ComfyUI workflow templates. Adds, replaces, validates, and audits thumbnails. Use when asked to: add a thumbnail, replace a preview image, update template image, fix missing thumbnail, check thumbnails, audit thumbnails, which templates need thumbnails, missing previews, add preview image, change template picture, update template visual, swap thumbnail, set thumbnail, upload preview, template image missing, broken thumbnail, thumbnail not showing. Triggers on: thumbnail, preview image, template image, template picture, missing thumbnail, add image, replace image, visual asset.

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Source SKILL.md: https://github.com/Comfy-Org/workflow_templates/blob/HEAD/.claude/skills/managing-thumbnails/SKILL.md

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Managing Thumbnails

This skill covers adding, replacing, validating, and auditing thumbnail images for ComfyUI workflow templates.

Naming Convention

Thumbnails live in templates/ alongside the workflow JSON files. They are named using the template's name field from templates/index.json:

Primary: {template_name}-1.webp
Secondary (optional): {template_name}-2.webp (only for dual-thumbnail variants)

The {template_name} portion must exactly match the name field in templates/index.json.

Supported Formats

Format	Notes
`.webp`	Preferred. Smallest file size. Use lossy compression (~65% quality).
`.png`	Acceptable fallback.
`.jpg` / `.jpeg`	Acceptable fallback.
`.webp` (animated)	Used for video-type templates (animated webp).

Thumbnail Variants

The thumbnailVariant field in templates/index.json controls how the thumbnail behaves on the site:

Variant	Thumbnails Needed	Effect
(none/default)	`-1` only	Static image, slight zoom on hover
`compareSlider`	`-1` AND `-2`	Before/after slider comparison
`hoverDissolve`	`-1` AND `-2`	Dissolves to second image on hover
`hoverZoom` / `zoomHover`	`-1` only	Same as default but zooms more

If a template uses compareSlider or hoverDissolve, both -1 and -2 files are required.

Adding a Thumbnail

Name the file {template_name}-1.webp, where {template_name} matches the template's name field in templates/index.json.
Place it in the templates/ directory.
Compress to a reasonable size (use lossy webp compression, ~65% quality).
If using compareSlider or hoverDissolve, also add {template_name}-2.webp.

Replacing a Thumbnail

Overwrite the existing file in templates/ with the new image, using the same filename.

Setting the Thumbnail Variant

Edit the template's entry in templates/index.json and set or change the thumbnailVariant field to one of: compareSlider, hoverDissolve, hoverZoom, or zoomHover. Remove the field (or leave it unset) for the default behavior.

Auditing Thumbnails

Run the validation script to check for issues:

python scripts/validate/validate_thumbnails.py

This checks for:

Templates missing their primary thumbnail
Templates with a dual-variant set (compareSlider or hoverDissolve) but missing the second thumbnail (-2)
Orphaned thumbnail files not referenced by any template

Site Preview Images

The site also generates workflow preview images via:

pnpm run generate:previews  # run from site/

These are separate from template thumbnails — they are auto-generated visualizations of the workflow graph, not the output images you manage here.

Validation After Changes

After adding, replacing, or modifying thumbnails, always validate:

python scripts/validate/validate_thumbnails.py
python scripts/validate/validate_templates.py

Then sync to packages:

python scripts/sync/sync_bundles.py

Rules

The template name in the filename must exactly match the name field in templates/index.json.
Always use .webp format when possible for smallest file size.
Thumbnails should ideally show the output produced by the workflow.
If the template uses compareSlider or hoverDissolve, both -1 and -2 files are required.
Never put thumbnails in site/ — they belong in templates/.
After adding or changing thumbnails, run python scripts/sync/sync_bundles.py to sync to packages.