nano-image-generate

# Nano Image Generator

Generate images using Nano Banana Pro (Gemini 3 Pro Preview) for any visual asset needs. Supports **reference images** for style transfer and character consistency.

## Quick Start

> [!IMPORTANT]
> **Path Check**: Before running, localize the `scripts/generate_image.py` file. If running this skill from another project, use the absolute path to the script or copy it to your project.

```bash
# Basic generation (saves to ./generated/)
# Ensure you are running this from the directory containing 'scripts/' OR provide full path
python scripts/generate_image.py "A friendly robot mascot waving"

# With style reference (keep same visual style)
python scripts/generate_image.py "Same style, new content" --ref ./reference.jpg --output ./new.png
```

## Model Selection

Choose the model based on user intent:

| Model | ID | Use Case | Keywords |
|-------|----|----------|----------|
| **Pro** | `gemini-3-pro-image-preview` | **Quality & Detail**. Default choice. Best for text, complex prompts, logos, and high-fidelity assets. | "high quality", "logo", "text", "detail", "complex" |
| **Flash** | `gemini-2.5-flash-image` | **Speed & Efficiency**. Best for rapid prototyping, large batches, or when low latency is critical. | "fast", "quick", "draft", "rapid" |

## Script Usage

```bash
python scripts/generate_image.py <prompt> --output <path> [options]
```

**Required:**
- `prompt` - Image description

**Options:**
- `--output, -o` - Output file path. Optional. Defaults to `./generated/<slug>.png`.
- `--model, -m` - Model selection: `pro` (default) or `flash`
- `--key, -k` - Gemini API Key (optional)
- `--aspect, -a` - Aspect ratio (default: `1:1`)
- `--size, -s` - Resolution: `1K`, `2K` (default), `4K`
- `--ref, -r` - Reference image (max 14)

## Examples

**High Quality Logo (Pro - Default):**
```bash
python scripts/generate_image.py "Futuristic company logo with text 'NANO'" --output ./logo.png
```

**Quick Prototype (Flash):**
```bash
python scripts/generate_image.py "Draft sketch of a cat" --model flash --output ./cat_draft.png
```

## Reference Images

Gemini supports up to **14 reference images** for:

### Style Transfer
Keep the visual style (colors, textures, mood) from a reference:
```bash
python scripts/generate_image.py "New scene with mountains, same visual style as reference" \
  --ref ./style-reference.jpg --output ./styled-mountains.png
```

### Character Consistency
Maintain character appearance across multiple images:
```bash
python scripts/generate_image.py "Same character now in a forest setting" \
  --ref ./character.png --output ./character-forest.png
```

### Multi-Image Fusion
Combine elements from multiple references:
```bash
python scripts/generate_image.py "Combine the style of first image with subject of second" \
  --ref ./style.png --ref ./subject.png --output ./combined.png
```

### Serial Image Generation (Batch Workflow)
For generating a series with consistent style:
1. Generate first image
2. Use first image as `--ref` for subsequent images
3. Each new image inherits the established style

```bash
# Generate cover
python scripts/generate_image.py "Tech knowledge card cover" -o ./01-cover.png

# Generate subsequent cards with style reference
python scripts/generate_image.py "Card 2 content, same style" --ref ./01-cover.png -o ./02-card.png
python scripts/generate_image.py "Card 3 content, same style" --ref ./01-cover.png -o ./03-card.png
```

## Directory Structure

To keep things organized, this skill uses a standard directory structure:

- `./generated/` - **Default output location**. Images are automatically saved here if no path is provided.
- `./assets/` - Recommended for storing reference images.

## Workflow

1. **Verify Output Directory & Script Path**:
   - Ensure the output directory exists (e.g., `mkdir -p generated`) or is writable.
   - Confirm the location of `generate_image.py`.

2. **Craft effective prompts** - Be specific and descriptive:
   - Include style: "flat design", "3D rendered", "watercolor", "minimalist"
   - Include context: "for a mobile app", "website hero image"
   - Include details: colors, mood, composition
   - For references: mention "same style as reference" or "keep the visual style"

3. **Choose appropriate settings:**
   - Icons/logos → `--aspect 1:1`
   - Banners/headers → `--aspect 16:9` or `21:9`
   - Mobile screens → `--aspect 9:16`
   - Xiaohongshu cards → `--aspect 3:4`
   - Photos → `--aspect 3:2` or `4:3`

## Examples

**App icon:**
```bash
python scripts/generate_image.py "Minimalist flat design app icon of a lightning bolt, purple gradient background, modern iOS style" \
  --output ./assets/app-icon.png --aspect 1:1
```

**Marketing banner:**
```bash
python scripts/generate_image.py "Professional website hero banner for a productivity app, abstract geometric shapes, blue and white color scheme" \
  --output ./public/images/hero-banner.png --aspect 16:9
```

**Xiaohongshu knowledge card:**
```bash
python scripts/generate_image.py "Tech knowledge card, dark blue purple gradient, neon cyan accents, code block style, Chinese text '标题'" \
  --output ./xiaohongshu/card.png --aspect 3:4
```

**Style transfer:**
```bash
python scripts/generate_image.py "Transform this photo into watercolor painting style" \
  --ref ./photo.jpg --output ./watercolor.png
```

**Character in new scene:**
```bash
python scripts/generate_image.py "Same character from reference, now sitting in a cafe, warm lighting" \
  --ref ./character.png --output ./character-cafe.png --aspect 3:2
```

## Prompt Tips

- **Be specific** - "A red apple on a wooden table" vs "an apple"
- **Include style** - "in the style of pixel art" or "photorealistic"
- **Mention purpose** - "for a children's book" affects the output style
- **Describe composition** - "centered", "rule of thirds", "close-up"
- **Specify colors** - Explicit color palettes yield better results
- **Reference prompts** - Use "same style as reference", "keep the visual aesthetic", "match the color palette"
- **Avoid** - Don't ask for complex text in images (use overlays instead)

## Limitations

- Maximum 14 reference images per request
- Text rendering may be imperfect (better to overlay text separately)
- Very specific brand logos may not reproduce exactly