Imported from majiayu000/claude-skill-registry-data (other/photo-to-slack-emoji/SKILL.md). Install upstream with npx skills add majiayu000/claude-skill-registry-data --skill photo-to-slack-emoji. Copyright stays with the author.

Photo to Slack Emoji Converter & Image Editor

Transform any photo into a classic Slack-optimized emoji using Google's Nano Banana Pro (Gemini 3 Pro Image) model with automatic subject identification and style transformation. NEW: Edit existing images with natural language prompts!

When to Use This Skill

Use this skill when:

• Converting photos into Slack custom emojis
• Editing existing images/emojis (add hats, change colors, add accessories, etc.)
• Creating icon-style representations of people, pets, objects, or concepts
• Need automatic subject identification and isolation
• Transforming photos to match classic emoji aesthetics (flat, simple, expressive)
• Ensuring Slack's strict 64KB file size and dimension requirements are met

Overview

This skill combines:

1. Google Nano Banana Pro (Gemini 3 Pro Image) - AI-powered subject identification, style transformation, and image editing with superior quality
2. Slack Emoji Validators - Ensures compliance with Slack's 64KB limit and optimal dimensions
3. Automatic Optimization - Color quantization, compression, and size validation

Two Main Workflows

1. Photo-to-Emoji Conversion (Original)

Photo Input → Gemini Identifies Subject → Transform to Emoji Style → Optimize for Slack → Validate

2. Image Editing (NEW!)

Existing Image → Natural Language Edit Prompt → Gemini Edits Image → Optimize (optional) → Save

How It Works

Photo Input → Gemini Identifies Subject → Transform to Emoji Style → Optimize for Slack → Validate

Workflow Steps:

1. Upload photo - Provide path to source image
2. AI identifies subject - Gemini's visual reasoning determines the main subject
3. Style transformation - Converts to emoji/icon/sticker style with descriptive prompt
4. Optimization - Reduces to 128x128, limits colors to 32-48, compresses to <64KB
5. Validation - Confirms Slack requirements are met

Quick Start

Basic Photo-to-Emoji Usage

from core.photo_to_emoji import convert_photo_to_emoji

# Convert a photo to a Slack emoji
convert_photo_to_emoji(
    input_path="~/Downloads/my_cat.jpg",
    output_path="~/Desktop/cat_emoji.png",
    style="classic_emoji",
    description="happy cat face"  # Optional: helps guide transformation
)

NEW: Image Editing Usage

IMPORTANT: Never override existing generated images. Always use a different output filename to preserve the original. Iterative editing works best when you can compare versions.

# Command line (easiest way)
python edit_image.py input.jpg output.png "add a party hat"
python edit_image.py cat_emoji.png cat_with_sunglasses.png "add cool sunglasses" --optimize

# WRONG: Don't overwrite the original
# python edit_image.py cat_emoji.png cat_emoji.png "edit" ❌

# CORRECT: Use a new filename
# python edit_image.py cat_emoji.png cat_emoji_edited.png "edit" ✅

# Python API
from core.gemini_client import GeminiImageClient

client = GeminiImageClient()

# Edit an existing image
with open("cat_emoji.png", "rb") as f:
    image_data = f.read()

edited_data = client.edit_image(
    image_data=image_data,
    mime_type="image/png",
    edit_prompt="add a party hat to the cat"
)

# Always save to a NEW filename
with open("cat_with_hat.png", "wb") as f:
    f.write(edited_data)

Advanced Usage with Custom Styles

convert_photo_to_emoji(
    input_path="~/Downloads/portrait.jpg",
    output_path="~/Desktop/person_emoji.png",
    style="flat_icon",
    description="friendly person waving",
    custom_prompt="Transform this photo into a simple, flat design icon with bold outlines, minimal details, solid colors, and a white background. Focus on the subject's key features and expression."
)

Available Styles

1. classic_emoji (Recommended for most use cases)

• Round, expressive, classic emoji aesthetic
• Simplified features with bold outlines
• High contrast, vibrant colors
• Perfect for faces, animals, and expressive subjects

Example prompt template:

Transform this photo into a classic emoji style: round shape, simplified features,
bold outlines, expressive and friendly, vibrant yellow/warm tones, minimal shading,
white or transparent background. Focus on the subject's main expression.

2. flat_icon

• Minimalist, flat design
• Simple geometric shapes
• Solid colors without gradients
• Best for objects, logos, symbols

Example prompt template:

Transform this photo into a flat, minimalist icon: simple geometric shapes,
solid colors, no gradients, bold clean outlines, modern flat design aesthetic,
white background. Capture the essence of the subject with minimal detail.

3. kawaii_sticker

• Cute, playful, Japanese kawaii aesthetic
• Rounded features, large eyes
• Pastel or vibrant colors
• Best for animals, characters, food

Example prompt template:

Transform this photo into a kawaii-style sticker: cute and playful, rounded features,
large expressive eyes, simple cel-shading, vibrant color palette, bold clean outlines,
white background. Make it adorable and friendly.

4. pixel_art

• Retro 8-bit/16-bit pixel art style
• Chunky pixels, limited color palette
• Nostalgic gaming aesthetic
• Best for characters, objects, icons

Example prompt template:

Transform this photo into pixel art: 16x16 or 32x32 pixel style, retro 8-bit aesthetic,
limited color palette (8-16 colors), chunky pixels, clear subject outline,
simple shading, transparent or solid background.

5. custom

• Provide your own transformation prompt
• Full control over style description
• Use for unique or specific aesthetic needs

API Configuration

Setting up Google Gemini API Key

You'll need a Google Gemini API key to use this skill.

1. Get API Key: Visit Google AI Studio
2. Set Environment Variable:

   export GEMINI_API_KEY="your-api-key-here"

3. Or provide directly in code:

   convert_photo_to_emoji(
       input_path="photo.jpg",
       output_path="emoji.png",
       api_key="your-api-key-here"
   )

API Costs

Google Gemini 2.5 Flash Image pricing:

• $30 per 1 million output tokens
• Each image = 1290 tokens (flat rate up to 1024x1024px)
• ~$0.039 per image generated

Very cost-effective for emoji creation!

Slack Requirements

Emoji Specifications (Strict)

• Max file size: 64KB (strict enforcement)
• Optimal dimensions: 128x128 pixels
• Recommended colors: 32-48 colors maximum
• Format: PNG with transparency support

Validation

The skill automatically validates and optimizes for these requirements:

from core.validators import validate_slack_emoji

# After conversion, validate
is_valid, report = validate_slack_emoji("emoji.png")

if is_valid:
    print("✅ Ready to upload to Slack!")
else:
    print(f"❌ Issues: {report}")

Examples

Example 1: Pet Photo to Emoji

# Convert a dog photo to a happy emoji
convert_photo_to_emoji(
    input_path="~/Photos/my_dog.jpg",
    output_path="~/Desktop/happy_dog_emoji.png",
    style="classic_emoji",
    description="happy golden retriever smiling"
)

Result: A round, simplified emoji-style dog face with expressive eyes and a big smile.

Example 2: Person Portrait to Icon

# Convert a headshot to a professional icon
convert_photo_to_emoji(
    input_path="~/Photos/headshot.jpg",
    output_path="~/Desktop/person_icon.png",
    style="flat_icon",
    description="professional person with glasses"
)

Result: A minimalist, flat design icon representation of the person.

Example 3: Food Photo to Kawaii Sticker

# Convert a pizza photo to cute sticker
convert_photo_to_emoji(
    input_path="~/Photos/pizza.jpg",
    output_path="~/Desktop/kawaii_pizza.png",
    style="kawaii_sticker",
    description="cute pizza slice with happy face"
)

Result: A kawaii-style pizza slice with adorable features.

Example 4: Batch Conversion

from core.photo_to_emoji import batch_convert

# Convert multiple photos at once
photos = [
    {"input": "cat.jpg", "output": "cat_emoji.png", "description": "happy cat"},
    {"input": "dog.jpg", "output": "dog_emoji.png", "description": "excited dog"},
    {"input": "bird.jpg", "output": "bird_emoji.png", "description": "singing bird"}
]

results = batch_convert(photos, style="classic_emoji")

Advanced Features

Custom Prompts

For maximum control, provide your own transformation prompt:

convert_photo_to_emoji(
    input_path="photo.jpg",
    output_path="emoji.png",
    style="custom",
    custom_prompt="""
    Transform this photo into a vintage cartoon style from the 1930s:
    thick black outlines, limited color palette (black, white, red, yellow),
    exaggerated features, bouncy and animated appearance, white background.
    """
)

Size Optimization Strategies

If your emoji exceeds 64KB after conversion:

from core.optimizer import aggressive_optimize

# Try aggressive optimization
aggressive_optimize(
    input_path="emoji.png",
    output_path="emoji_optimized.png",
    target_size_kb=60,  # Leave buffer below 64KB
    strategies=["reduce_colors", "reduce_dimensions", "compress_png"]
)

Preview Before Upload

from core.preview import preview_emoji

# Preview how it will look in Slack
preview_emoji("emoji.png", sizes=[16, 32, 64, 128])

Shows how the emoji appears at different sizes (Slack displays emojis at various scales).

Troubleshooting

Issue: File size exceeds 64KB

Solutions:

1. Use fewer colors: max_colors=32 instead of 48
2. Simplify the style: "flat_icon" compresses better than "kawaii_sticker"
3. Reduce detail in description: Less detail = simpler image = smaller file
4. Use aggressive optimization (see Advanced Features)

Issue: Subject not identified correctly

Solutions:

1. Provide more specific description parameter
2. Crop photo to focus on main subject before conversion
3. Use better-lit, clearer source photo
4. Try a custom prompt with explicit subject description

Issue: Style doesn't match expectation

Solutions:

1. Try different style presets (flat_icon vs classic_emoji)
2. Use custom_prompt for precise control
3. Add more descriptive terms to description parameter
4. Review style examples in /templates/style_examples.md

Issue: API authentication fails

Solutions:

1. Verify GEMINI_API_KEY environment variable is set
2. Check API key is valid at Google AI Studio
3. Ensure no extra spaces or quotes in API key
4. Try providing api_key parameter directly

File Structure

~/.claude/skills/photo-to-slack-emoji/
├── skill.md                    # This file
├── core/
│   ├── photo_to_emoji.py      # Main conversion logic
│   ├── gemini_client.py       # Gemini API wrapper
│   ├── optimizer.py           # Image optimization utilities
│   ├── validators.py          # Slack requirement validators
│   └── preview.py             # Preview utilities
├── templates/
│   ├── style_prompts.json     # Pre-defined style templates
│   └── style_examples.md      # Visual style guide
└── references/
    ├── gemini-api-docs.md     # Gemini API documentation
    └── slack-emoji-specs.md   # Slack emoji specifications

Dependencies

# Required packages
pip install pillow google-genai requests

# Optional for advanced features
pip install imageio numpy

Best Practices

1. Start with high-quality photos - Better input = better output
2. Use descriptive filenames - Helps with organization in Slack
3. NEVER override existing generated images - Always save edits to new filenames to preserve originals
4. Test at multiple sizes - Preview before uploading to ensure clarity
5. Keep it simple - Simpler styles compress better and meet size limits
6. Provide context - Use the description parameter to guide transformation
7. Batch process - Convert multiple photos at once for efficiency
8. Iterative editing - Make small edits and save each version with descriptive names (e.g., cat_v1.png, cat_v2_hat.png, cat_v3_final.png)

Limitations

• API rate limits - Google Gemini has rate limits (check your quota)
• Subject complexity - Very complex subjects may not simplify well
• Background removal - Gemini does its best, but manual editing may improve results
• Transparent backgrounds - Not always perfect; may need manual cleanup
• Text in photos - May not preserve text accurately in emoji transformation

Related Skills

• slack-gif-creator - Create animated GIFs for Slack
• canvas-design - Design custom graphics from scratch
• firecrawl-mcp - Scrape emoji images from web for reference

What's Next

After creating your emoji:

1. Upload to Slack:

   • Go to Slack workspace settings
   • Click "Customize" → "Emoji"
   • Upload your PNG file
   • Give it a memorable name like :my_cat: or :happy_dog:

2. Share with team:

   • Emojis are available to entire workspace
   • Use in messages, reactions, and status updates

3. Create variations:

   • Try different styles for the same photo
   • Experiment with descriptions for different expressions
   • Build an emoji library for your team

Feedback & Support

This skill uses:

• Google Gemini 2.5 Flash Image (aka Nano Banana) - Documentation
• Slack Emoji Guidelines - Slack Help Center

For issues or suggestions, check the skill's GitHub repository or the Claude Code skills directory.