Video Thumbnail Generator

Video Thumbnail Generator

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

Non-Negotiables

• 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.

• 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.

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

Workflow

• 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.
• Read project state, transcript, and available media context.
• Inspect candidate frames:
• expressive face
• product or UI clearly visible
• dramatic action moment
• clean composition
• strong lighting or clear subject separation
• Classify the thumbnail job:
• talking-head / opinion / tutorial
• product / software / demo
• cinematic / documentary / art
• entertainment / challenge / reaction
• education / business / concept
• Propose concise title text options.
• 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.
• Generate thumbnail options using selected real frames and the selected style.
• Check mobile readability, subject fidelity, product/UI truthfulness, and visual contrast.
• 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.