Nano Banana Pro OpenRouter

Overview

google/gemini-3-pro-image-preview

Prompt-only generation

uv run {baseDir}/scripts/generate_image.py \
  --prompt "A cinematic sunset over snow-capped mountains" \
  --filename sunset.png

Edit a single image

uv run {baseDir}/scripts/generate_image.py \
  --prompt "Replace the sky with a dramatic aurora" \
  --input-image input.jpg \
  --filename aurora.png

Compose multiple images

uv run {baseDir}/scripts/generate_image.py \
  --prompt "Combine the subjects into a single studio portrait" \
  --input-image face1.jpg \
  --input-image face2.jpg \
  --filename composite.png

Resolution

• Use

  --resolution

  with

  1K

  ,

  2K

  , or

  4K

  .
• Default is

  1K

  if not specified.

System prompt customization

assets/SYSTEM_TEMPLATE

Behavior and constraints

• Accept up to 3 input images via repeated

  --input-image

  .

• --filename

  accepts relative paths (saves to current directory) or absolute paths.
• If multiple images are returned, append

  -1

  ,

  -2

  , etc. to the filename.
• Print

  MEDIA: <path>

  for each saved image. Do not read images back into the response.

Troubleshooting

OPENROUTER_API_KEY is not set

$env:OPENROUTER_API_KEY = "sk-or-..."

export OPENROUTER_API_KEY="sk-or-..."

uv: command not found

AuthenticationError