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commands/promptgen.md

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+# Promptgen Command
+
+Transform simple descriptions into detailed, optimized image generation prompts using Gemini 2.0 Flash AI.
+
+## Usage
+
+```bash
+gemini-nano-banana-tool promptgen DESCRIPTION [OPTIONS]
+```
+
+## Arguments
+
+- `DESCRIPTION` - Simple description to enhance (e.g., "wizard cat", "cyberpunk city")
+
+## Options
+
+- `-t, --template TEXT` - Apply specialized template (photography, character, scene, food, abstract, logo)
+- `-s, --style TEXT` - Style hint (photorealistic, artistic, minimalist, etc.)
+- `-o, --output PATH` - Save prompt to file instead of stdout
+- `--json` - Output in JSON format
+- `-v, --verbose` - Show analysis and reasoning
+- `--list-templates` - Show all available templates
+
+## Examples
+
+### Basic Usage
+
+```bash
+# Generate detailed prompt from simple description
+gemini-nano-banana-tool promptgen "wizard cat"
+
+# With template for better results
+gemini-nano-banana-tool promptgen "wizard cat" --template character
+
+# Save to file for reuse
+gemini-nano-banana-tool promptgen "sunset landscape" -o prompt.txt
+```
+
+### Pipeline: Generate Prompt → Create Image
+
+```bash
+# Single pipeline: description → optimized prompt → image
+gemini-nano-banana-tool promptgen "wizard cat in magical library" | \
+  gemini-nano-banana-tool generate --stdin -o wizard-cat.png -a 16:9
+```
+
+### With Templates
+
+```bash
+# Photography template - technical camera details
+gemini-nano-banana-tool promptgen "mountain landscape" --template photography
+
+# Food template - plating and lighting
+gemini-nano-banana-tool promptgen "pasta dish" --template food
+
+# Scene template - foreground/midground/background
+gemini-nano-banana-tool promptgen "cyberpunk city" --template scene
+```
+
+### JSON Output (for automation)
+
+```bash
+# Get structured output
+gemini-nano-banana-tool promptgen "sunset" --json
+
+# Output format:
+# {
+#   "original": "sunset",
+#   "prompt": "A breathtaking golden hour sunset...",
+#   "template": null,
+#   "style": null,
+#   "tokens_used": 156
+# }
+```
+
+## Available Templates
+
+- `photography` - Professional photography with technical details (aperture, focal length, lighting)
+- `character` - Character design with pose, attire, expression
+- `scene` - Scene composition with foreground/midground/background layers
+- `food` - Food photography with plating, garnish, lighting
+- `abstract` - Abstract art with shapes, colors, patterns
+- `logo` - Logo design with typography, symbolism, brand identity
+
+## Why Use Promptgen?
+
+Creating effective image generation prompts requires knowledge of:
+- Photography and composition terminology
+- Lighting and technical details
+- Artistic styles and techniques
+- Color theory and palettes
+
+Promptgen automates this expertise using AI, transforming simple ideas into detailed, effective prompts.
+
+## Output Modes
+
+- **Plain text** (default) - Ready for piping to generate command
+- **JSON** (`--json`) - Structured output for scripts and automation
+- **Verbose** (`-v`) - Shows AI analysis and reasoning process
+
+## Cost
+
+Promptgen uses Gemini 2.0 Flash for prompt generation:
+- Cost: ~$0.001-0.003 per prompt optimization
+- Much cheaper than trial-and-error generation
+
+## Authentication
+
+Requires `GEMINI_API_KEY` or `GOOGLE_API_KEY` environment variable.
+
+Get your API key: https://aistudio.google.com/app/apikey