video-thumbnail-generator

name	video-thumbnail-generator
description	Create platform-ready thumbnails from real video frames. Use when the user wants a thumbnail, cover image, YouTube cover, Shorts cover, Bilibili cover, Xiaohongshu cover, or other video poster image.

Video Thumbnail Generator

Use this skill to create a high-clarity thumbnail or cover image from the actual video content.

Non-Negotiables

1. Use the real video as visual evidence.

   • If the thumbnail shows a person, product, UI, frame, or scene from the video, extract or inspect real frames.
   • Never invent a generic software interface, fake product screen, or unrelated person.

2. Read style references before recommending styles.

   • Use references/thumbnail-styles.md and references/thumbnail-style-recipes.md.
   • Only offer style directions supported by those references or by the user's explicit instruction.

3. Keep text short and readable.

   • Usually 2-5 words.
   • Avoid thin type, low contrast, small labels, and clutter.

Workflow

1. Confirm platform and aspect ratio if missing.
   • YouTube / Bilibili: usually 16:9.
   • Shorts / TikTok / Douyin: usually 9:16.
   • Xiaohongshu / WeChat Channels: usually 3:4.
   • Correct ambiguous ratio language gently, especially 4:3 vs 3:4.
2. Read project state, transcript, and available media context.
3. Inspect candidate frames:
   • expressive face
   • product or UI clearly visible
   • dramatic action moment
   • clean composition
   • strong lighting or clear subject separation
4. Classify the thumbnail job:
   • talking-head / opinion / tutorial
   • product / software / demo
   • cinematic / documentary / art
   • entertainment / challenge / reaction
   • education / business / concept
5. Propose concise title text options.
6. Offer 3-6 clearly different style directions.
   • Each option should name the composition, not only a channel/style label.
   • Exclude weak options.
   • Wait for user choice when the direction is not obvious.
7. Generate thumbnail options using selected real frames and the selected style.
8. Check mobile readability, subject fidelity, product/UI truthfulness, and visual contrast.
9. Present results and offer targeted adjustments.

Prompt Shape

[Platform] thumbnail, [aspect ratio / dimensions], [style name].

COMPOSITION: [subject position, scale, background, graphic balance]
REAL REFERENCE: [describe selected frame zone by zone]
TEXT: "[short title]" in [high-contrast style]
STYLE: [one-line style recipe from references]
CONSTRAINTS: readable at mobile size, no fake UI, no watermark, no play button.

References

• references/thumbnail-styles.md: style library from real thumbnail analysis.
• references/thumbnail-style-recipes.md: quick style recipes and prompt patterns.
• references/field-testing-notes.md: known failure modes.