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Opc-skills banner-creator

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.

install
source · Clone the upstream repo
git clone https://github.com/ReScienceLab/opc-skills
Claude Code · Install into ~/.claude/skills/
T=$(mktemp -d) && git clone --depth=1 https://github.com/ReScienceLab/opc-skills "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/banner-creator" ~/.claude/skills/resciencelab-opc-skills-banner-creator && rm -rf "$T"
manifest: skills/banner-creator/SKILL.md
source content

Banner Creator Skill

Create professional banners through AI image generation with an iterative design process.

Prerequisites

Required API Keys (set in environment):

Required Skills:

  • nanobanana
    - AI image generation (Gemini 3 Pro Image)

File Output Location

All generated files should be saved to the 

.skill-archive
directory:

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

Example:

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

Workflow

Step 1: Discovery & Requirements

Before generating, gather requirements from user:

Ask about:

  1. Purpose - Where will the banner be used?

    • GitHub README
    • Twitter/X header
    • LinkedIn banner
    • Website hero
    • YouTube channel art

  2. Target ratio/size - See references/formats.md:

    • 2:1
      (1280x640) - GitHub README
    • 3:1
      (1500x500) - Twitter header
    • 16:9
      (1920x1080) - Website hero

  3. Style preference:

    • Match existing logo/brand?
    • Pixel art / 8-bit retro
    • Minimalist / flat design
    • Gradient / modern
    • Illustrated / artistic

  4. Content elements:

    • Brand name / project name?
    • Tagline / slogan?
    • Logo character to include?

  5. Color preferences:

    • Existing brand colors?
    • Let AI decide?

Wait for user confirmation before proceeding!

Step 2: Generate Banner Variations

Generate 20 banner variations using the 

nanobanana
skill:

# 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

Guidelines:

  • Generate at 
    21:9
    ratio (widest available), crop later to target
  • Use batch_generate.py for multiple variations (includes auto-delay)
  • Use sequential naming: 
    banner-01.png
    , 
    banner-02.png
    , etc.

Image Editing (for incorporating existing logo):

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

Step 3: Create HTML Preview

Copy the preview template and open in browser:

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

Then open in default browser:

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

IMPORTANT: Update the HTML to include the correct number of banners generated.

Step 4: Iterate with User

Ask user which banners they prefer:

  • "Which banners do you like? (e.g., #3, #7, #15)"
  • "What do you like about them?"
  • "Any changes you'd want?"

Based on feedback:

  1. Generate 10-20 more variations of favorite styles
  2. Use naming: 
    banner-{original}-v{n}.png
    (e.g., 
    banner-03-v1.png
    )
  3. Update HTML preview
  4. Repeat until user selects final banner

Step 5: Crop to Target Ratio

Once user approves a banner, crop to target size:

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

Common targets:

  • GitHub README: 
    --ratio 2:1 --width 1280
    → 1280x640
  • Twitter header: 
    --ratio 3:1 --width 1500
    → 1500x500
  • Website hero: 
    --ratio 16:9 --width 1920
    → 1920x1080

Step 6: Deliver Final Assets

Present final deliverables:

## 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.

Quick Reference

Common Prompt Patterns

With Text:

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

With Character:

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

Abstract/Gradient:

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

Scene-based:

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

Supported Aspect Ratios

Generate at widest ratio, then crop:

  • 21:9
    - Ultra-wide (recommended for generation)
  • 16:9
    - Wide
  • 3:2
    - Standard wide

References