Fast Thumbnail (vipsthumbnail)

Generate thumbnails at high throughput using vipsthumbnail. Distinct from fast-resize: this is purpose-built for "make small previews of every image in this folder" workflows where output is always a downscale and quality is "good enough for a thumbnail".

When to use

• Building a contact-sheet / web-gallery / index of an image library.
• Pre-rendering thumbnails for a UI / filesystem browser.
• Bulk-shrinking large originals to share / archive.

Do not use this skill when:

• The user wants the same size as the originals — that's a no-op.
• The user is upscaling — use fast-resize (or upscale-image for AI upscale).
• The user wants to keep original quality — this skill assumes lossy thumbnail-grade output.

Inputs