Banner Creator

What it does

When your agent uses it

• User wants to create a banner
• Tasks that involve Image generation
• Tasks that involve Social media graphics

Example prompts

• “/banner-creator”

Requirements

• Python 3
• A credential in GEMINI_API_KEY

Workflow steps

6 steps, taken from the step headings in SKILL.md.

1. 1Discovery & Requirements
2. 2Generate Banner Variations
3. 3Create HTML Preview
4. 4Iterate with User
5. 5Crop to Target Ratio
6. 6Deliver Final Assets

What it can do on your machine

Read from SKILL.md and the folder at commit 8295f4a. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 1 file in scripts/ (Python, from the files we listed), which the agent can run.

  Shell commands in SKILL.md call:

  • python3

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • aistudio.google.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names these keys or tokens, usually read from environment variables:

  • GEMINI_API_KEY

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Banner Creator loads about 1.3k tokens when it runs, and up to ~1.9k if it reads all its reference files. Until then it costs about 68 tokens; SKILL.md has 364 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~68

When it runs · the whole SKILL.md, loaded when a task matches

~1.3k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~1.9k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from ReScienceLab/opc-skills at commit 8295f4a, republished under its Apache-2.0 licence (© ReScienceLab). 364 words, ~1,340 tokens.

name

banner-creator

description

Create banners using AI image generation. Discuss format/style, generate variations, iterate with user feedback, crop to target ratio. Use when user wants to create a banner, header, hero image, cover image, GitHub banner, Twitter header, or readme banner.

.skill-archive/banner-creator/<yyyy-mm-dd-summaryname>/

.skill-archive/banner-creator/2026-01-19-opc-banner/
  banner-01.png
  banner-02.png
  ...
  banner-03-cropped.png
  preview.html

# Generate single banner
python3 <nanobanana_skill_dir>/scripts/generate.py "{style} banner for {brand}, {description}, {text elements}" \
  --ratio 21:9 -o .skill-archive/banner-creator/<date-name>/banner-01.png

# Batch generate 20 banners
python3 <nanobanana_skill_dir>/scripts/batch_generate.py "{style} banner for {brand}, {description}, {text elements}" \
  -n 20 --ratio 21:9 -d .skill-archive/banner-creator/<date-name> -p banner

python3 <nanobanana_skill_dir>/scripts/generate.py "add {logo character} to the left side of the banner" \
  -i /path/to/existing-logo.png --ratio 21:9 -o banner-with-logo.png

cp <skill_dir>/templates/preview.html .skill-archive/banner-creator/<yyyy-mm-dd-summaryname>/preview.html

open .skill-archive/banner-creator/<yyyy-mm-dd-summaryname>/preview.html

python3 <skill_dir>/scripts/crop_banner.py {input.png} {output.png} --ratio 2:1 --width 1280

## Final Banner Assets

| File | Description | Size |
|------|-------------|------|
| banner-03.png | Original (21:9) | 2016x864 |
| banner-03-cropped.png | GitHub README (2:1) | 1280x640 |

All files saved to: `.skill-archive/banner-creator/<yyyy-mm-dd-summaryname>/`
Copy final banner to user's desired location.

Wide banner for {brand}, {style} style, featuring "{text}" prominently displayed, {colors}, {scene/elements}

Wide banner featuring {character description}, {style} style, {scene}, text "{brand name}" on {position}, {colors}

Abstract {style} banner, {colors} gradient, geometric patterns, modern tech feel, text "{brand}" centered

{Style} illustration banner, {scene description}, {character} in {action}, "{brand}" text overlay, {colors}

© ReScienceLab, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 16 other files (scripts, references) in skills/banner-creator of ReScienceLab/opc-skills.

• SKILL.md
• .claude-plugin/plugin.json
• examples/images/banner-01.png
• examples/images/banner-02.png
• examples/images/banner-03.png
• examples/images/banner-04.png
• examples/images/banner-05.png
• examples/images/banner-06.png
• examples/images/github-banner-01.png
• examples/images/github-banner-02.png
• examples/images/github-banner-03.png
• examples/images/opc-banner-final.png
• examples/opc-banner-creation.md
• references/formats.md
• scripts/crop_banner.py
• templates
• … and 1 more

Open the folder on GitHubat commit 8295f4a