Gemini OpenAI format (Images)

curl --request POST \
  --url https://api.gravitex.ai/v1/images/generations

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.gravitex.ai/v1/images/generations",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://api.gravitex.ai/v1/images/generations"

	req, _ := http.NewRequest("POST", url, nil)

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

require 'uri'
require 'net/http'

url = URI("https://api.gravitex.ai/v1/images/generations")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)

response = http.request(request)
puts response.read_body

POST

images

generations

Gemini OpenAI format (Images)

curl --request POST \
  --url https://api.gravitex.ai/v1/images/generations

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.gravitex.ai/v1/images/generations",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://api.gravitex.ai/v1/images/generations"

	req, _ := http.NewRequest("POST", url, nil)

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

require 'uri'
require 'net/http'

url = URI("https://api.gravitex.ai/v1/images/generations")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)

response = http.request(request)
puts response.read_body

For native generateContent image generation, see Gemini Native (Image). For extra_body.google fine control, use /v1/chat/completions via Gemini OpenAI format (Chat) (see appendix).

Gemini imagine models (including Google “nano banana” and other multimodal image models that return text + image) are available on Gravitex AI via OpenAI-compatible /v1/images/generations and /v1/images/edits. Base URL: https://api.gravitex.ai

Authentication
Models
Endpoints
/v1/images/generations — Text-to-image / image-to-image
- [Request parameters](#Request parameters)
- image Field格式
- size / quality mapping
- [Response format](#Response format)
[/v1/images/edits — Image edits](#v1imagesedits—Image edits)
Examples
- 1. Text-to-image
- 2. Image-to-image / style transfer
- [3. Multi-image blend](#3-Multi-image blend)
- [4. /v1/images/edits equivalent call](#4-v1imagesedits-equivalent call)
- 5. Python (OpenAI SDK)
- 6. Node.js (OpenAI SDK)
Errors
Billing
LimitationDescription
[Best practices](#Best practices)
常见Issue
Appendix: vs /v1/chat/completions

Authentication

所有Endpoint使用 Bearer Token Authentication。在 Gravitex AI 控制台创建令牌后，在请求头中添加：

Authorization: Bearer sk-{your_token_key}

Use JSON:

Content-Type: application/json

Models

模型 ID	Description	Image-to-image	Default size
`gemini-3-pro-image-preview`	Gemini 3 Pro image preview — highest quality	✅	1024×1024 / 2K
`gemini-3.1-flash-image-preview`	Gemini 3.1 Flash image preview — fast, cost-effective (“nano banana”)	✅	1024×1024
`gemini-2.5-flash-image`	Gemini 2.5 Flash image — stable	✅	1024×1024

More imagine models are added over time — see the console model list.

Endpoints

Endpoint	Method	Purpose
`/v1/images/generations`	POST	文生图、图生图、Multi-image blend
`/v1/images/edits`	POST	Image edits（与 generations Protocol等价，由 SDK 习惯决定走哪个）

对 imagine 模型来说，/v1/images/generations 与 /v1/images/edits 完全等价——传不传 image Field决定是文生图还是图生图，而不是Endpoint路径。选哪个看你用的 SDK 习惯（OpenAI Python SDK 中 images.generate vs images.edit）。

`/v1/images/generations` — Text-to-image / image-to-image

POST https://api.gravitex.ai/v1/images/generations

Request parameters

Parameter	Type	Required	Default	Description
`model`	string	是	—	模型 ID，见 Models
`prompt`	string	是	—	Text prompt describing the image
`image`	string / string[]	否	—	Input参考图（图生图、风格迁移、Multi-image blend用），格式见 `image` Field格式
`size`	string	否	由模型决定	期望尺寸或宽高比，见 `size` / `quality` mapping
`quality`	string	否	`auto`	Output质量档位，见 `size` / `quality` mapping
`n`	integer	否	`1`	Ignored: one image per upstream call; loop client-side for multiple
`response_format`	string	否	`b64_json`	当前不Passthrough：响应永远以 `b64_json` Field返回 base64

`image` Field格式

image Field用于”图生图”——把一张或多张参考图喂给模型作为视觉上下文。支持以下两种 JSON 形态：

// (1) Single: string
{ "image": "https://example.com/cat.jpg" }
{ "image": "data:image/png;base64,iVBORw0KGgo..." }
{ "image": "iVBORw0KGgo..." }   // raw base64 (must be valid image)

// (2) Multiple: string array
{ "image": [
    "https://example.com/a.jpg",
    "data:image/png;base64,iVBORw0KGgo..."
] }

URL 形态：网关会自动 fetch 并校验图片Type；URL 必须可公网访问，建议用 https。
base64 / data URI: gateway decodes and sniffs MIME.
Supported formats: image/png、image/jpeg、image/jpg、image/webp、image/heic、image/heif。
Not supported multipart/form-data 上传文件——请把图片转成 base64 或先上传到对象存储拿到 URL。

`size` / `quality` mapping

imagine 模型的Output有限定档位（不像传统模型可任意指定像素），网关会自动把 OpenAI 风格的mapping到模型支持的档位。

`size` → aspect ratio

`size` 取值	aspectRatio
`256x256`、`512x512`、`1024x1024`	`1:1`（square）
`1536x1024`	`3:2`（landscape）
`1024x1536`	`2:3`（portrait）
`1024x1792`	`9:16`（phone portrait）
`1792x1024`	`16:9`（widescreen）
Pass ratio directly (`9:16`, `16:9`, etc.)	原样使用
Omitted or unknown	Model default (usually `1:1`)

`quality` → imageSize tier

`quality` 取值	imageSize	Notes
`hd`、`high`、`2K`	`2K`	Higher resolution, larger/slower
`standard`、`medium`、`low`、`auto`、`1K`、未传	`1K`	Standard, faster

Response format

Success response

{
  "created": 1747299537,
  "data": [
    {
      "url": "",
      "b64_json": "iVBORw0KGgoAAAANSUhEUgAA...",
      "revised_prompt": "好的，我已为您生成了一只穿唐装写春联的柴犬..."
    }
  ],
  "metadata": {
    "text": "好的，我已为您生成了一只穿唐装写春联的柴犬..."
  },
  "usage": {
    "total_tokens": 1421,
    "input_tokens": 27,
    "output_tokens": 1394,
    "input_tokens_details": {
      "text_tokens": 27,
      "image_tokens": 0
    },
    "output_tokens_details": {
      "image_tokens": 1290,
      "text_tokens": 104
    }
  }
}

Field	Type	Description
`created`	integer	Unix timestamp (seconds)
`data[].b64_json`	string	Base64 image (no `data:` prefix) — decode to PNG
`data[].url`	string	当前为空字符串（保留兼容Field，平台不上传图片到外部 URL）
`data[0].revised_prompt`	string	Model description / revised prompt (text + image)
`metadata.text`	string	Duplicate of `revised_prompt` for simpler clients
`usage.total_tokens`	integer	Total tokens
`usage.input_tokens`	integer	Input tokens (prompt + reference images)
`usage.output_tokens`	integer	Output tokens (image + description text)
`usage.input_tokens_details.text_tokens`	integer	Input text tokens
`usage.input_tokens_details.image_tokens`	integer	Input image tokens (0 if no reference)
`usage.output_tokens_details.image_tokens`	integer	Output image tokens (per-model fixed cost)
`usage.output_tokens_details.text_tokens`	integer	Output text tokens

Gemini imagine 模型在生成图片的同时常常会返回一段文字描述（“我帮您画了 X”），这段文字以 revised_prompt + metadata.text 形式返回，客户端可选择展示。 usage Field格式与 OpenAI gpt-image-1 完全对齐，方便用 OpenAI SDK 的项目无缝接入。

Error response

{
  "error": {
    "message": "request blocked by Gemini API: SAFETY",
    "type": "invalid_request_error",
    "code": "prompt_blocked"
  }
}

详见 Errors 章节。

`/v1/images/edits` — Image edits

POST https://api.gravitex.ai/v1/images/edits 请求/Response format与 /v1/images/generations 完全一致（同样接受 JSON + image Field，返回相同结构）。区别仅在于 OpenAI Python SDK 中 images.edit 与 images.generate 是两个不同的Method，部分用户习惯按”编辑”语义走 edits 入口。

⚠️ 与 OpenAI 官方 dall-e-2 的 /images/edits 不同：本EndpointNot supported multipart/form-data 上传 + mask Field（imagine 模型靠 prompt 指挥编辑，不需要 mask）。image Field同 generations。

Examples

1. Text-to-image

Basic usage: prompt only.

curl -X POST https://api.gravitex.ai/v1/images/generations \
  -H "Authorization: Bearer sk-your_token_key" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3.1-flash-image-preview",
    "prompt": "Shiba inu in Tang suit writing spring couplets, ink wash style",
    "size": "1024x1024",
    "quality": "hd"
  }'

2. Image-to-image / style transfer

把一张照片改成赛博朋克风格——image Field传单张参考图。

curl -X POST https://api.gravitex.ai/v1/images/generations \
  -H "Authorization: Bearer sk-your_token_key" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3.1-flash-image-preview",
    "prompt": "Cyberpunk style, neon, rainy street",
    "size": "16:9",
    "quality": "hd",
    "image": "https://example.com/portrait.jpg"
  }'

Or base64 / data URI (local files):

curl -X POST https://api.gravitex.ai/v1/images/generations \
  -H "Authorization: Bearer sk-your_token_key" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3.1-flash-image-preview",
    "prompt": "Anime character style",
    "image": "data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/..."
  }'

3. Multi-image blend

把多张参考图合成到一张图里——image Field传字符串数组。

curl -X POST https://api.gravitex.ai/v1/images/generations \
  -H "Authorization: Bearer sk-your_token_key" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-2.5-flash-image",
    "prompt": "Both characters on a sunset beach",
    "size": "16:9",
    "image": [
      "https://example.com/character-a.png",
      "https://example.com/character-b.png"
    ]
  }'

4. `/v1/images/edits` equivalent call

Same as example 2, via edits:

curl -X POST https://api.gravitex.ai/v1/images/edits \
  -H "Authorization: Bearer sk-your_token_key" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3.1-flash-image-preview",
    "prompt": "Cyberpunk style",
    "image": "https://example.com/portrait.jpg"
  }'

5. Python (OpenAI SDK)

import base64
from openai import OpenAI

client = OpenAI(
    api_key="sk-your_token_key",
    base_url="https://api.gravitex.ai/v1",
)

# 文生图
resp = client.images.generate(
    model="gemini-3.1-flash-image-preview",
    prompt="一只穿唐装在写春联的柴犬，水墨风格",
    size="1024x1024",
    quality="hd",
)

img_b64 = resp.data[0].b64_json
print("revised_prompt:", resp.data[0].revised_prompt)

# 保存为本地 PNG
with open("output.png", "wb") as f:
    f.write(base64.b64decode(img_b64))

图生图（OpenAI SDK 的 images.edit 在我们这里也走 generations Protocol；如要走 /v1/images/edits 入口，请用 client.images.edit(...)）：

# I2I via generations (recommended):
# OpenAI SDK 的 images.generate 不直接支持 image Field，
# use HTTP POST:
import httpx
resp = httpx.post(
    "https://api.gravitex.ai/v1/images/generations",
    headers={"Authorization": "Bearer sk-your_token_key"},
    json={
        "model": "gemini-3.1-flash-image-preview",
        "prompt": "Cyberpunk neon style",
        "image": "https://example.com/portrait.jpg",
    },
    timeout=60,
).json()
print(resp["data"][0]["b64_json"][:80] + "...")

6. Node.js (OpenAI SDK)

import OpenAI from "openai";
import { writeFile } from "fs/promises";

const client = new OpenAI({
  apiKey: "sk-your_token_key",
  baseURL: "https://api.gravitex.ai/v1",
});

// 文生图
const resp = await client.images.generate({
  model: "gemini-3.1-flash-image-preview",
  prompt: "一只穿唐装在写春联的柴犬，水墨风格",
  size: "1024x1024",
  quality: "hd",
});

const b64 = resp.data[0].b64_json!;
await writeFile("output.png", Buffer.from(b64, "base64"));
console.log("revised_prompt:", resp.data[0].revised_prompt);

I2I with fetch:

const r = await fetch("https://api.gravitex.ai/v1/images/generations", {
  method: "POST",
  headers: {
    "Authorization": "Bearer sk-your_token_key",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    model: "gemini-3.1-flash-image-preview",
    prompt: "Cyberpunk style",
    image: "https://example.com/portrait.jpg",
  }),
});
const data = await r.json();

Errors

On failure, HTTP ≠ 200:

{
  "error": {
    "message": "...",
    "type": "...",
    "code": "..."
  }
}

Common error codes

HTTP	`code`	Description	Action
`400`	`prompt_blocked`	Blocked by Gemini safety (violence, sensitive content)	Change prompt or reference image
`400`	`invalid_request`	模型不在 imagine 列表里、`prompt` 为空、`image` Field格式不对、参考图 MIME 不在白名单等	Fix per error message
`401`	`invalid_authentication`	Invalid or expired token	Create a new key
`402`	`insufficient_quota`	Insufficient quota	Top up or contact admin
`429`	`rate_limit_exceeded`	触发速率Limitation	Backoff per `Retry-After`
`502`	`empty_response`	Upstream 200 but no image (rare)	Retry 1–2 times, then support
`503`	`bad_response`	Upstream unavailable	Retry with backoff
`504`	`request_timeout`	Upstream timeout	Retry

prompt_blocked often means sensitive topics — rephrase prompt.

Billing

按”实际生成的图片张数”计费：上游真实返回了几张图就扣几张，请求里的 n Parameter不影响计费（见 LimitationDescription）。
**No charge when blocked or zero images.
See console pricing per model/quality.
计费明细可在 令牌使用记录 页查看，每条记录包含 生成数量 N Field。

LimitationDescription

Limitation项	Description
`n` 被忽略	One image per call; loop N times for N images
No streaming	`/v1/images/generations` 与 `/v1/images/edits` 都是非StreamingEndpoint，没有 SSE chunk
No multipart upload	No `multipart/form-data`；`image` Field必须是 JSON 字符串（URL / base64 / data URI）
`response_format` Always `b64_json`	No hosted URL — upload base64 yourself
`mask` FieldNo	imagine 模型靠 prompt 指挥编辑，不需要 mask；OpenAI 官方 dall-e-2 的 mask Protocol在本Endpoint无效
Reference image ≤ 8 MB recommended	过大的Input图会增加处理耗时，并可能触发 HTTP body size Limitation
Input MIME must be allowlisted	png / jpeg / jpg / webp / heic / heif; other formats (bmp, tiff, gif) error
≤ 4 reference images recommended	Multi-image blend时图越多耗时越长，超过 4 张请权衡延迟
本Endpoint下No `extra_body`	Use `/v1/chat/completions` for `imageConfig` / `safetySettings` / `thinking_config` (appendix)

Best practices

prompt: be specific (style, color, composition, camera); avoid vague words.
**Start I2I with ≤512×512 references, then full size.
多次Retry：图像生成有随机性，同一 prompt 可能首次效果不理想，建议提供”重新生成”按钮让用户多试几次。
**Add regenerate/report for sensitive topics.
**Persist b64_json immediately — no upstream cache.
**Show revised_prompt as free UX copy under the image.
**Draft at 1K, final at 2K to save cost.

常见Issue

Q1：Why `n=4` returns one image?

A：Gemini imagine 模型上游单次调用只产出 1 张图，平台会按实际产出张数计费。需要多张请客户端多次调用，每次单独计费。

Q2：Can I mask regions for I2I?

A：imagine 模型No mask Field，所有改动通过 prompt 描述（如”只把头发改成红色，其它保持不变”）。模型会理解 prompt 自动定位区域。

Q3：No `data:` prefix on `b64_json`?

A：b64_json 是纯 base64 字符串，方便直接 decode 保存为文件。如果你要嵌入 HTML <img src>，自己拼接前缀即可："data:image/png;base64," + b64_json。

Q4：Images only, no text?

A：当前不能——imagine 模型的特色就是图文一起返回，revised_prompt/metadata.text Field可以选择不展示，但请求层面无法关闭。

Q5：Same price for T2I and I2I?

A：是的——按”Output图片张数 + Output quality 档位”计费，与是否带 image Field无关。

Q6：Text + multiple reference images?

A：可以。image Field支持 string[]，配合 prompt 描述融合方式，参考 [场景 3：Multi-image blend](#3-Multi-image blend)。

Q7：generations vs chat for imagine?

A：详见附录。简单来说：

/v1/images/generations：Protocol简单（OpenAI Image API 标准），适合”我只要图片”的场景。
/v1/chat/completions：能控制 Gemini 原生Parameter（imageConfig、safetySettings、thinking_config 等），适合”需要细粒度控制”的场景。

Appendix: vs `/v1/chat/completions`

Gemini imagine 模型同时也可以走 OpenAI 的 /v1/chat/completions Endpoint（把 prompt 写成 message，把图片放进 content 数组）。两个入口对比：

Aspect	`/v1/images/generations` & `/v1/images/edits`	`/v1/chat/completions`
Protocol	OpenAI Image API（轻量）	OpenAI Chat Completions API（功能丰富）
Input	`prompt` + `image` Field	`messages[].content`（多模态数组）
Output	`data[].b64_json` + `revised_prompt`	`choices[].message.content`（数组：text + image_url）
Streaming	❌ No	❌ imagine 模型在 chat 入口下也强制非Streaming
`extra_body` Passthrough	❌ No	✅ 通过 `extra_body.google.*` 完全Passthrough Gemini 原生Parameter
Multi-turn context	❌ Single request	✅ Multi-turn `messages`
Best for	One-shot images, batch scripts, DALL·E-compatible clients	对话式交互（“再改一下”）、需要原生Parameter（`imageConfig`/`safetySettings`/`thinking_config`）

Chat endpoint example (Gemini OpenAI Chat):

curl -X POST https://api.gravitex.ai/v1/chat/completions \
  -H "Authorization: Bearer sk-your_token_key" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3.1-flash-image-preview",
    "messages": [
      { "role": "user", "content": [
          { "type": "text", "text": "Cyberpunk style" },
          { "type": "image_url", "image_url": { "url": "https://example.com/portrait.jpg" } }
        ]
      }
    ],
    "extra_body": {
      "google": {
        "generationConfig": {
          "imageConfig": { "aspectRatio": "16:9", "imageSize": "2K" }
        }
      }
    }
  }'

返回的 choices[0].message.content 是数组：

[
  { "type": "text", "text": "Done, here is your edit..." },
  { "type": "image_url", "image_url": {
      "url": "data:image/png;base64,iVBORw0KGgo...",
      "mime_type": "image/png"
  } }
]

​Contents

​Authentication

​Models

​Endpoints

​/v1/images/generations — Text-to-image / image-to-image

​Request parameters

​image Field格式

​size / quality mapping

​size → aspect ratio

​quality → imageSize tier

​Response format

​Success response

​Error response

​/v1/images/edits — Image edits

​Examples

​1. Text-to-image

​2. Image-to-image / style transfer

​3. Multi-image blend

​4. /v1/images/edits equivalent call

​5. Python (OpenAI SDK)

​6. Node.js (OpenAI SDK)

​Errors

​Common error codes

​Billing

​LimitationDescription

​Best practices

​常见Issue

​Q1：Why n=4 returns one image?

​Q2：Can I mask regions for I2I?

​Q3：No data: prefix on b64_json?

​Q4：Images only, no text?

​Q5：Same price for T2I and I2I?

​Q6：Text + multiple reference images?

​Q7：generations vs chat for imagine?

​Appendix: vs /v1/chat/completions

Contents

Authentication

Models

Endpoints

`/v1/images/generations` — Text-to-image / image-to-image

Request parameters

`image` Field格式

`size` / `quality` mapping

`size` → aspect ratio

`quality` → imageSize tier

Response format

Success response

Error response

`/v1/images/edits` — Image edits

Examples

1. Text-to-image

2. Image-to-image / style transfer

3. Multi-image blend

4. `/v1/images/edits` equivalent call

5. Python (OpenAI SDK)

6. Node.js (OpenAI SDK)

Errors

Common error codes

Billing

LimitationDescription

Best practices

常见Issue

Q1：Why `n=4` returns one image?

Q2：Can I mask regions for I2I?

Q3：No `data:` prefix on `b64_json`?

Q4：Images only, no text?

Q5：Same price for T2I and I2I?

Q6：Text + multiple reference images?

Q7：generations vs chat for imagine?

Appendix: vs `/v1/chat/completions`