UNIVERSAL CHATGPT THUMBNAIL INSTRUCTION v3.0

A general-purpose HTML instruction document for generating a final thumbnail except for vertical cropping. This version adds full-band utilization and message completeness requirements.

Purpose

Guarantee that every generated image is a complete usable thumbnail, already correct horizontally as 16:9, requiring only vertical cropping by height adjustment, with no dependency on top or bottom space.

Core Rule

Generate the image as a COMPLETE 16:9 thumbnail
embedded inside a taller canvas.

ALL important content MUST exist inside a centered
horizontal band that is already 16:9.

The rest of the image (top and bottom) must be fully discardable.

Geometry Requirement

Let W = full image width

Define a centered horizontal band such that:

BandWidth  = W
BandHeight = W * (9/16)

This band MUST contain the FULL thumbnail.

Top and bottom areas:
- must contain NO important content
- must be safe to remove entirely

Cropping Guarantee

The image MUST remain fully correct if:

- width is unchanged
- height is reduced to match the 16:9 band

No horizontal repositioning allowed.
No manual alignment allowed.

Content Rules

Only ONE thumbnail concept per image.

NO:
- grids
- collages
- side-by-side panels
- multiple thumbnails

Everything must form ONE unified image inside the band.

Text Rules

Text is optional.

If used:
- must be fully inside the 16:9 band
- must remain readable after crop
- must not touch or depend on edges

Band Utilization Requirement

Inside the 16:9 band:

- ALL horizontal space must be actively used
- NO large empty or low-information areas allowed
- The band must appear visually full edge-to-edge

The viewer must immediately perceive:
- content across LEFT, CENTER, RIGHT
- no dead zones
- no unused background areas

Message Completeness Rule

If multiple messages are requested:

- ALL messages MUST appear inside the band
- NONE may be omitted
- NONE may be reduced to background elements

Messages must be:
- clearly visible
- spatially distributed across the band
- readable at thumbnail size

Failure to include ALL required messages = automatic rejection

Band Density Test

Before returning the image, verify:

"Does the 16:9 band contain dense, edge-to-edge information,
or are there empty or low-detail regions?"

If ANY of the following exist → REJECT:

- large flat background areas
- unused corners
- empty horizontal space
- text clustered only in one region

The band must feel packed and complete.

Automatic Failure Conditions

Reject output if:

- important content exists above or below band
- multiple panels or sections exist
- cropping removes critical elements
- composition relies on full canvas height
- thumbnail is not already complete inside band
- the band is not fully utilized
- required messages are missing or unreadable

Execution Instruction

1. Generate image
2. Identify central 16:9 band

3. Test A:
   "If I remove top and bottom right now,
    is this already a finished thumbnail?"

4. Test B:
   "Does the band use FULL horizontal space?"

5. Test C:
   "Are ALL required messages present and readable?"

6. If ANY answer = NO → regenerate
7. If ALL = YES → return image

Absolute Rule

The generator is NOT allowed to rely on the user to fix layout.

The image must already be correct BEFORE cropping.

What This Solves

  • Template mismatch
  • Manual alignment
  • Unusable top or bottom content
  • Trial-and-error geometric correction
  • Weak band utilization
  • Missing required messages

Final Definition

The generated image is:

A finished thumbnail, already correct,
simply revealed by cropping vertically,
with the 16:9 band fully utilized and complete.

Universal ChatGPT Thumbnail Instruction v3.0 • HTML document