Image Generator Skill

A Claude Code skill for generating and editing images using Google's Gemini model (gemini-3-pro-image-preview), with advanced transparent PNG support via triangulation matting.

Features

• Text-to-Image: Generate images from text descriptions (1K/2K/4K, multiple aspect ratios)
• Image Editing: Edit 1-14 images with natural language instructions
• Transparent PNG: Two strategies for true alpha transparency:
  • Triangulation Matting — mathematically precise, handles semi-transparent effects (glows, gradients, shadows)
  • rembg AI — fast single-pass removal for solid-edge subjects
• Smart Mode Selection: Auto-detects which transparency method to use based on prompt keywords
• Smart Background Colors: 6-color palette with conflict avoidance to prevent subject-background clashing
• Files API: Resumable upload for large images to avoid base64 timeouts

Setup

1. Get a free API key from Google AI Studio

2. Configure the key (choose one):

   Option A — Environment variable (recommended):

   export GEMINI_API_KEY="your_api_key_here"

   Option B — .env file:

   cp .claude/skills/image-generator/.env.example .claude/skills/image-generator/.env
   # Edit .env and add your key

3. (Optional) Set GEMINI_BASE_URL to route requests through a proxy.

Scripts

All scripts live in .claude/skills/image-generator/scripts/:

Script	Purpose
generate_image.sh	Text-to-image generation
edit_image.sh	Edit/compose 1-14 images
upload_file.sh	Upload image via Files API (resumable)
triangulation_gen.sh	Transparent PNG via triangulation matting
transparent_png.py	Post-processing: alpha extraction from images
env_setup.sh	Shared config loader (sourced by all scripts)

Quick Examples

Generate an image:

bash .claude/skills/image-generator/scripts/generate_image.sh \
  --prompt "A minimalist logo for a coffee shop" \
  --output logo.png --size "2K" --aspect "1:1"

Edit an image:

bash .claude/skills/image-generator/scripts/edit_image.sh \
  --prompt "Add a sunset background" \
  --image photo.png --output edited.png

Transparent PNG (triangulation):

bash .claude/skills/image-generator/scripts/triangulation_gen.sh \
  --prompt "A glowing crystal orb" \
  --bg1 "#FFFFFF" --bg2 "#000000" \
  --output crystal.png --size "1K" --aspect "1:1"

Remove background (rembg):

python3 .claude/skills/image-generator/scripts/transparent_png.py \
  input.png output.png --use-rembg

Dependencies

# Core
pip install google-genai pillow

# Transparent PNG post-processing
pip install numpy scipy

# AI background removal (optional)
pip install rembg

System requirements: Python 3.10+, Bash, curl

How Transparent PNG Works

Gemini cannot natively output RGBA. This skill works around the limitation:

Triangulation Matting (best quality)

1. Generate the image on background color A (e.g., red)
2. Edit the same image to background color B (e.g., blue)
3. Compute exact alpha per-pixel: alpha = 1 - (I_A - I_B) / (A - B)
4. Recover true foreground color: F = (I - (1-alpha) * B) / alpha

rembg AI (simpler)

1. Generate with chroma key green background
2. Run pre-trained AI model to remove background

The skill auto-selects the method based on prompt keywords (e.g., "glow", "gradient" triggers triangulation).

Resolution Reference

Aspect Ratio	1K	2K	4K
1:1	1024x1024	2048x2048	4096x4096
16:9	1376x768	2752x1536	5504x3072
9:16	768x1376	1536x2752	3072x5504

License

Internal skill — not for redistribution.