Nano Banana Pro 在线生图：Google Gemini 3 Pro Image，单张 $0.09

import base64
import mimetypes
import os
import sys

import requests

API_KEY = os.environ.get("LAOZHANG_API_KEY")
if not API_KEY:
    raise RuntimeError("Set the LAOZHANG_API_KEY environment variable before running this example.")

API_URL = "https://api2.laozhang.ai/v1beta/models/gemini-3-pro-image:generateContent"
REQUEST_TIMEOUT_SECONDS = 500

headers = {
    "Authorization": f"Bearer {API_KEY}",
    "Content-Type": "application/json",
}

payload = {
    "contents": [{
        "parts": [
            {"text": "设计导向音频产品的高级活动主视觉，工业细节准确，棚拍反射受控，具有电影感空间层次。"}
        ]
    }],
    "generationConfig": {
        "responseModalities": ["IMAGE"],
        "imageConfig": {
            "imageSize": "2K"
        }
    }
}

try:
    response = requests.post(
        API_URL,
        headers=headers,
        json=payload,
        timeout=REQUEST_TIMEOUT_SECONDS,
    )
except requests.Timeout as error:
    print(
        "Request timed out after 500 seconds. The result status may be unknown; "
        "check call and billing logs before retrying.",
        file=sys.stderr,
    )
    raise SystemExit(1) from error

if response.status_code != 200:
    print(f"API error {response.status_code}: {response.text}", file=sys.stderr)
    raise SystemExit(1)

try:
    result = response.json()
except ValueError as error:
    print("API returned a non-JSON response.", file=sys.stderr)
    raise SystemExit(1) from error

if not isinstance(result, dict):
    print("API returned an unexpected JSON shape.", file=sys.stderr)
    raise SystemExit(1)

image_part = None
for candidate in result.get("candidates", []):
    for part in candidate.get("content", {}).get("parts", []):
        inline_data = part.get("inlineData") or part.get("inline_data")
        if inline_data and inline_data.get("data"):
            image_part = inline_data
            break
    if image_part:
        break

if not image_part:
    response_id = result.get("responseId", "not provided")
    print(f"No image data in response. responseId={response_id}", file=sys.stderr)
    raise SystemExit(1)

mime_type = image_part.get("mimeType") or image_part.get("mime_type") or "image/png"
encoded_image = image_part["data"]
if encoded_image.startswith("data:"):
    header, encoded_image = encoded_image.split(",", 1)
    mime_type = header[5:].split(";", 1)[0] or mime_type

extension_by_mime = {
    "image/jpeg": "jpg",
    "image/png": "png",
    "image/webp": "webp",
    "image/gif": "gif",
}
extension = extension_by_mime.get(mime_type, "bin")
output_path = f"output.{extension}"

with open(output_path, "wb") as output_file:
    output_file.write(base64.b64decode(encoded_image, validate=True))

print(f"Image saved: {output_path} ({mime_type})")