Image Generation with imagen CLI
Generate images using the imagen CLI — a unified interface for Google Gemini and OpenAI image models. Supports text prompts, multiple aspect ratios, output formats, batch generation, and more.
Prerequisites
- imagen CLI: Install via
curl -fsSL https://raw.githubusercontent.com/ozten/imagen/main/scripts/install.sh | bash - API Keys: Configure via environment variables or config file (see below)
Quick Start
# Basic generation (uses default nano-banana / gemini-3-pro-image-preview)
imagen "A cat wearing a top hat" -o cat.jpg
# With aspect ratio
imagen "Mountain panorama" --aspect-ratio 16:9 -o mountains.jpg
# Using OpenAI model
imagen "Cyberpunk cityscape" -m gpt-1.5 -o city.png
# Multiple images
imagen "Abstract art" -n 3 -o art.jpg
# Higher resolution
imagen "Detailed landscape" --size 2K -o landscape.jpg
# Read prompt from file
imagen --prompt-file prompt.txt -o result.jpgModels
| Alias | Model ID | Provider |
|---|---|---|
nano-banana (default) | gemini-3-pro-image-preview | Gemini |
gpt-1.5 | gpt-image-1.5 | OpenAI |
gpt-1 | gpt-image-1 | OpenAI |
gpt-1-mini | gpt-image-1-mini | OpenAI |
Options
| Option | Values | Default | Description |
|---|---|---|---|
-m, --model | see Models table | nano-banana | Image generation model |
-a, --aspect-ratio | 1:1, 16:9, 9:16, 4:3, 3:4, etc. | 1:1 | Output aspect ratio |
-s, --size | 1K, 2K, 4K | 1K | Image resolution |
-q, --quality | auto, low, medium, high | auto | Quality (OpenAI models only) |
-f, --format | jpeg, png, webp | jpeg | Output format |
-o, --output | path | auto-generated | Output file path |
-n, --count | integer | 1 | Number of images to generate |
-p, --prompt-file | path | none | Read prompt from file |
-v, --verbose | flag | off | Verbose output |
Workflow
If the user provides $ARGUMENTS, treat them as the image prompt. Otherwise ask what they'd like to generate.
Step 0: Check imagen is installed
Before generating, verify imagen is available:
which imagenIf imagen is NOT found:
- Tell the user that the
imagenCLI is required but not installed - Ask them: "Would you like me to install the
imagenCLI? It's a lightweight Rust binary from https://github.com/ozten/imagen" - If they agree, run:
curl -fsSL https://raw.githubusercontent.com/ozten/imagen/main/scripts/install.sh | bash - After installation, verify it worked:
imagen --version
If API keys are NOT configured:
Check for API keys:
# Check env vars
echo "${GEMINI_API_KEY:+gemini_ok}" "${OPENAI_API_KEY:+openai_ok}"
# Check config file
cat ~/.config/imagen/config.toml 2>/dev/nullIf no keys are found for the provider needed by the chosen model:
- Tell the user which API key is needed (Gemini for nano-banana, OpenAI for gpt-* models)
- Ask them to set up keys via environment variable or config file:
- Environment variable: export GEMINI_API_KEY="your-key" or export OPENAI_API_KEY="your-key" - Config file (~/.config/imagen/config.toml): [keys] gemini = "your-gemini-api-key" openai = "your-openai-api-key"
- Do NOT proceed with generation until at least one relevant key is configured
Step 1: Generate the image
Determine the prompt, output path, model, aspect ratio, and other options, then run:
imagen "PROMPT" \
--model MODEL \
--aspect-ratio ASPECT_RATIO \
--size SIZE \
--format FORMAT \
--output OUTPUT_PATHOnly include flags that differ from defaults.
Step 2: Report results
Report the output file path and parameters used. If generation fails, check:
- API key is configured for the chosen provider
- Prompt doesn't violate content policies
- Model alias is valid
Batch Generation
For multiple images, either use -n for the same prompt or run imagen multiple times with different prompts:
# Same prompt, multiple variations
imagen "Abstract art" -n 3 -o abstract.jpg
# Different prompts in sequence
imagen "Panel 1: A sunny beach" -o panel_1.jpg
imagen "Panel 2: Same beach at sunset" -o panel_2.jpgIntegration
Other skills and pipelines can delegate image generation to this skill by invoking the imagen CLI directly.