Imagen Skill Reference

Setup

1. Get a Gemini API Key

Go to Google AI Studio
Click "Get API Key"
Create a new API key or use an existing one

2. Set Environment Variable

Windows (PowerShell):

$env:GEMINI_API_KEY = "your-api-key-here"

# To persist across sessions, add to your PowerShell profile:
Add-Content $PROFILE "`n`$env:GEMINI_API_KEY = 'your-api-key-here'"

Windows (CMD):

set GEMINI_API_KEY=your-api-key-here

# To persist, use System Properties > Environment Variables

macOS/Linux:

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

# Add to ~/.zshrc or ~/.bashrc to persist
echo 'export GEMINI_API_KEY="your-api-key-here"' >> ~/.zshrc

API Reference

Model

Model ID: gemini-3-pro-image-preview (configurable via --model flag or GEMINI_MODEL env var)
Endpoint: https://generativelanguage.googleapis.com/v1beta/models/{model}:streamGenerateContent

Image Sizes

Size	Description
`512`	512x512 pixels - Fast, good for icons/thumbnails
`1K`	1024x1024 pixels - Default, balanced quality/speed
`2K`	2048x2048 pixels - High resolution, slower

Script Parameters

Python Script (Cross-Platform)

python scripts/generate_image.py <prompt> [output_path] [--size SIZE]

Parameter	Required	Default	Description
`prompt`	Yes	-	Text description of desired image
`output_path`	No	`./generated-image.png`	Where to save the image
`--size`	No	`1K`	Image size (512, 1K, or 2K)

Environment Variables

Variable	Required	Default	Description
`GEMINI_API_KEY`	Yes	-	Your Google Gemini API key
`IMAGE_SIZE`	No	`1K`	Image size (512, 1K, or 2K)

Usage Examples

Basic Generation

python scripts/generate_image.py "A serene mountain landscape at dawn"

Custom Output Path

python scripts/generate_image.py "Minimalist logo design" "./assets/logo.png"

High Resolution

python scripts/generate_image.py --size 2K "Detailed portrait" "./high-res.png"

Small/Fast Generation

python scripts/generate_image.py --size 512 "Simple icon" "./icon.png"

Prompt Tips

For Best Results

Be specific: "A red sports car" vs "A cherry red 1967 Mustang convertible"
Include style: "in watercolor style", "photorealistic", "minimalist flat design"
Mention lighting: "golden hour lighting", "soft diffused light", "dramatic shadows"
Specify composition: "close-up", "wide angle", "from above", "centered"

Advanced Prompting Techniques

These techniques produce significantly better results for photorealistic and professional imagery:

Camera & Lens Specifications

Include specific photography parameters for authentic looks:

Lens focal length: "85mm f/1.4 lens", "50mm prime", "35mm wide angle"
Aperture: "shallow depth of field at f/1.8", "deep focus at f/8"
Camera angle: "eye-level shot", "low angle looking up", "3/4 profile view"

Example: "Portrait shot with 85mm f/1.4 lens, shallow depth of field, subject sharp against soft bokeh background"

Lighting Architecture

Specify complete lighting setups for professional results:

Three-point lighting: key light, fill light, rim/back light
Catchlights: reflections in eyes for portraits
Shadow quality: "soft shadows", "dramatic hard shadows", "subtle rim light"

Example: "Professional headshot with three-point lighting setup, soft key light from left, subtle fill light, rim light for hair separation, visible catchlights in eyes"

Film Stock & Era Aesthetics

Reference specific film stocks or eras for authentic period looks:

Film stocks: "Kodak Portra 400 color palette", "Fujifilm Pro 400H tones", "Kodak Tri-X grain"
Era aesthetics: "1990s disposable camera quality", "early-2000s digital camera look", "1970s Polaroid style"
Grain and texture: "subtle film grain", "realistic sensor noise"

Example: "Casual portrait with Kodak Portra 400 color tones, natural film grain, 1990s aesthetic, soft warm highlights"

Facial Consistency (for portraits/people)

When generating or editing images with faces, explicitly state preservation requirements:

"Keep the facial features exactly consistent"
"Preserve original face structure and proportions"
"Do not alter or change the face"

Material & Texture Details

Add realistic texture specifications:

Skin: "natural skin texture with visible pores", "subtle skin imperfections"
Fabric: "fine wool texture visible", "silk sheen and drape"
Surfaces: "brushed metal finish", "weathered wood grain"

Example: "Close-up portrait showing natural skin texture with visible pores, fine fabric detail on collar, realistic hair strands"

Composition Framing

Be precise about framing and subject positioning:

Shot types: "chest-up framing", "3/4 body shot", "full body"
Positioning: "centered subject", "rule of thirds placement", "mirror selfie angle"
Aspect ratio context: "portrait orientation", "landscape format", "square crop"

Example Prompts by Use Case

UI/Frontend:

"A modern dashboard UI mockup with dark theme, showing analytics charts"
"Clean minimalist app icon for a task management app, rounded square shape"
"Hero image for a SaaS landing page, abstract gradient with geometric shapes"

Documentation:

"Simple architecture diagram showing microservices connected by arrows"
"Flowchart illustrating user authentication process"

Placeholders:

"Professional headshot placeholder, silhouette style, neutral gray background"
"Product image placeholder, simple box shape with 'Image Coming Soon' text"

Marketing/Creative:

"Isometric illustration of a modern office workspace"
"Gradient abstract background suitable for presentation slides"

Professional Portraits (using advanced techniques):

"Corporate headshot, 85mm f/2.8 lens, three-point studio lighting, navy blue suit, neutral gray backdrop, subtle catchlights, chest-up framing, natural skin texture"
"Casual lifestyle portrait, Kodak Portra 400 tones, natural window light, soft shadows, 3/4 body shot, authentic film grain, early-2000s digital aesthetic"

E-commerce & Product Photography:

"Product photo of leather watch, 100mm macro lens, soft diffused lighting, visible leather texture and stitching, clean white background, subtle reflection"
"Fashion flat-lay, overhead shot, soft natural lighting, fabric texture visible, minimalist composition"

Troubleshooting

"GEMINI_API_KEY not set"

Ensure the environment variable is set in your current shell: