Banner Creator Agent Skill

Banner Creator Skill

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

Prerequisites

Required API Keys (set in environment):

• GEMINI_API_KEY - Get from Google AI Studio

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:

• Purpose - Where will the banner be used?
• GitHub README
• Twitter/X header
• LinkedIn banner
• Website hero
• YouTube channel art

• Target ratio/size - See references/formats.md:
• 2:1 (1280x640) - GitHub README
• 3:1 (1500x500) - Twitter header
• 16:9 (1920x1080) - Website hero

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

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

• 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:

• Generate 10-20 more variations of favorite styles
• Use naming: banner-{original}-v{n}.png (e.g., banner-03-v1.png)
• Update HTML preview
• 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

• references/formats.md - Common banner sizes by platform
• examples/opc-banner-creation.md - Full example conversation