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BytesAgain β€Ί Skills β€Ί OpenRouter Image Generation
πŸ¦€ ClawHub

OpenRouter Image Generation

by @yangwenyu2

Generate images using Google Gemini via OpenRouter API. Supports text-to-image and reference-image-guided generation. Use when the user asks to generate, cre...

Versionv1.0.0
Downloads906
Installs10
#clawhub
TERMINAL
clawhub install openrouter-image-gen

πŸ“– About This Skill

name: gemini-image-gen description: Generate images using Google Gemini via OpenRouter API. Supports text-to-image and reference-image-guided generation. Use when the user asks to generate, create, draw, or design images/illustrations/covers/avatars.

Gemini Image Generation

Generate images via google/gemini-3.1-flash-image-preview on OpenRouter. Cheap ($0.25/M in, $1.5/M out), fast, good quality.

Quick Start

python3 scripts/generate.py "a watercolor illustration of a cozy cafΓ©" -o output.png

With reference image (style/character guidance): 

python3 scripts/generate.py "same character but waving hello" -o wave.png --ref reference.png

Script path: skills/gemini-image-gen/scripts/generate.py

Requirements

  • OPENROUTER_API_KEY environment variable (or --api-key flag)
  • Python 3.10+ (stdlib only, no pip installs needed)

    • How It Works

    1. Calls OpenRouter /chat/completions with modalities: ["text", "image"] 2. Optionally encodes a reference image as base64 in the message 3. Extracts generated image from choices[0].message.images[0].image_url.url (data:image/png;base64,...) 4. Decodes and saves to output path

    Prompt Engineering Tips (from experience)

    Aspect Ratio & Composition

  • Gemini respects aspect ratio instructions in the prompt
  • For vertical (e.g. phone wallpaper, Xiaohongshu cover): add "vertical composition, 3:4 aspect ratio"
  • For horizontal (e.g. banner): add "horizontal composition, 16:9 aspect ratio"
  • For square: add "square composition, 1:1 aspect ratio"
  • Always specify β€” without it, Gemini defaults to roughly square and may crop awkwardly

    • Character Consistency

  • When using --ref, describe the character features explicitly in the prompt AND provide the reference image
  • Key details to specify: hair color/style, eye color, clothing, accessories, expression
  • Example: "same character from reference: silver-to-ice-blue gradient shoulder-length hair, ice-blue eyes, cream cardigan over light blue shirt, snowflake earring"
  • Gemini is decent at maintaining consistency but drifts on small details β€” always re-specify distinguishing features

    • Style Control

  • Name the art style explicitly: "soft watercolor illustration", "anime cel-shading", "photorealistic", "flat vector", "oil painting"
  • For warm/cozy tone: "warm color palette, cream and peach gradient background, bokeh light spots"
  • For dark/moody: "dark gradient background, deep navy to black, subtle glow effects"
  • Mentioning a well-known art style works: "in the style of Studio Ghibli", "Makoto Shinkai lighting"

    • Text in Images

  • Gemini can render short text in images but it's unreliable for CJK characters
  • For English text: works reasonably well if you specify font style ("bold sans-serif", "handwritten script")
  • For Chinese/Japanese: avoid β€” it usually garbles characters. Add text overlays with a separate tool (e.g. ImageMagick, Pillow) instead

    • Common Pitfalls

  • Body proportions: Gemini sometimes compresses/distorts figures. Add "natural human body proportions, do not squash or stretch" for character art
  • Hands: Still a weak spot. Minimize visible hands or describe hand pose explicitly
  • Multiple subjects: More than 2-3 subjects increases inconsistency. Keep scenes focused
  • Batch generation: For generating multiple variations, run the script multiple times β€” each call is independent. Do NOT ask for "4 options" in one prompt

    • Sending Images on Feishu

    ⚠️ Critical: Images must be saved to a path within localRoots (typically your OpenClaw workspace dir). /tmp is NOT whitelisted on Feishu.

    # Save to workspace, not /tmp
output_path = "my_image.png"  # relative to workspace
    Send via message tool:
    

      media: "file:///my_image.png"
    

      (use 'media' parameter, NOT 'filePath')

    After sending, clean up temporary images to avoid workspace clutter.

    Advanced: Calling from Python (without CLI)

    import os, sys
sys.path.insert(0, "skills/gemini-image-gen/scripts")
from generate import generate
    generate(
    prompt="a cute robot reading a philosophy book",
    output="robot.png",
    ref_image=None,  # or path to reference image
)

    Model Alternatives

    | Model | Cost | Notes | |-------|------|-------| | google/gemini-3.1-flash-image-preview | $0.25/$1.5 per M tokens | Default. Best balance of cost and quality | | google/gemini-3.1-pro-preview | $2/$12 per M tokens | Higher quality but 8x more expensive | | openai/gpt-image-1 | varies | OpenAI's image model, different API format β€” not supported by this script |

    Troubleshooting

  • "No image in response": Check .debug.json file created alongside output. Usually means the prompt triggered safety filters or the model returned text-only.
  • Garbled/distorted output: Try rephrasing. Add "high quality, detailed" and be more specific about composition.
  • API error 429: Rate limited. Wait 30s and retry.
  • API error 402: Insufficient credits on OpenRouter.

    • πŸ’‘ Examples

    python3 scripts/generate.py "a watercolor illustration of a cozy cafΓ©" -o output.png

    With reference image (style/character guidance): 

    python3 scripts/generate.py "same character but waving hello" -o wave.png --ref reference.png

    Script path: skills/gemini-image-gen/scripts/generate.py

    πŸ“‹ Tips & Best Practices

  • "No image in response": Check .debug.json file created alongside output. Usually means the prompt triggered safety filters or the model returned text-only.
  • Garbled/distorted output: Try rephrasing. Add "high quality, detailed" and be more specific about composition.
  • API error 429: Rate limited. Wait 30s and retry.
  • API error 402: Insufficient credits on OpenRouter.