# Workflow Utilities Pick Image By Index API

> Chọn ảnh thứ N từ danh sách URL ảnh bằng chỉ mục bắt đầu từ 1 và quy tắc dự phòng

Trả về một ảnh từ mảng URL ảnh. `index` bắt đầu từ 1, nên 1 là ảnh đầu tiên. Khi chỉ mục vượt quá độ dài danh sách, `fallback_index` quyết định trả về ảnh đầu tiên hay cuối cùng. Hữu ích khi nối các bước trong workflow.

- Model id: `workflow-utilities/pick-image-by-index`
- Made by: Utility
- Category: Image Editing
- Output: image
- Estimated price per run: $0.001 / run (cheapest run $0.001 (1 API credit))
- Run: `POST https://api.doitong.com/v1/run/workflow-utilities/pick-image-by-index`
- Quote: `POST https://api.doitong.com/v1/quote/workflow-utilities/pick-image-by-index`
- Docs page: https://doitong.com/vi/developers/models/workflow-utilities/pick-image-by-index

## Pricing

Price: **$0.001 / run**. Estimated from the typical cost of one run. The quote is exactly what the run charges.

The full example input below costs $0.001 = 1 API credit (1 request × 1 API credits).

Prices are the upstream price in USD, paid from the API balance in API credits (1000 API credits = 1 USD). `POST https://api.doitong.com/v1/quote/workflow-utilities/pick-image-by-index` with the same JSON body returns the exact price for that input; the quote is exactly what a run charges. Invalid input is never charged and failed or canceled requests are refunded automatically.

## Input parameters

Send either the canonical name or the native field name (not both). Canonical names are the same across models.

| Parameter | Canonical name | Type | Required | Default | Allowed values / range | Description |
|---|---|---|---|---|---|---|
| `image_urls` | `images` | array of image URL | yes |  |  | Mảng URL hình ảnh dùng làm nguồn lựa chọn. |
| `index` |  | integer | yes |  |  | Chọn hình ảnh theo vị trí, đếm từ 1: yêu cầu 1 cho hình ảnh đầu tiên, 2 cho hình ảnh thứ hai và tiếp tục tương tự. |
| `fallback_index` |  | enum (string) | no | `first-image` | `first-image`, `last-image` | Chính sách chọn hình ảnh ngoài phạm vi, mặc định là `first-image`; bị bỏ qua với `index` hợp lệ, còn việc xác thực vẫn thất bại nếu `index` nhỏ hơn 1 hoặc mảng `image_urls` rỗng. Chỉ `index` vượt quá độ dài mảng mới kích hoạt chính sách: `first-image` chọn hình ảnh đầu tiên, còn `last-image` chọn hình ảnh cuối cùng. |

File parameters (`images`) take a public `https://` URL, a `data:` URI up to 10 MB, or the `file_url` of an upload from `POST /files`.

## Example input

Required parameters only:

```json
{
  "images": [
    "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
  ],
  "index": 1
}
```

A fuller example:

```json
{
  "image_urls": [
    "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
  ],
  "index": 1
}
```

## Run it

Set `DOITONG_API_KEY` to a key from https://doitong.com/developers/dashboard#keys. `?wait=20` returns the finished request in the same call when it is ready within 20 seconds; otherwise poll `GET /requests/{id}` (it also accepts `?wait=`), or pass `webhook_url`.

### curl

```bash
# Run the model; wait up to 20 s for the finished result in the same call
curl -X POST "https://api.doitong.com/v1/run/workflow-utilities/pick-image-by-index?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "image_urls": [
      "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
    ],
    "index": 1
  }'

# Still "queued" or "running"? Poll with the id from the response:
curl "https://api.doitong.com/v1/requests/REQUEST_ID?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY"
```

### JavaScript

```javascript
const API = "https://api.doitong.com/v1";
const headers = {
  "Authorization": "Bearer " + process.env.DOITONG_API_KEY,
  "Content-Type": "application/json",
};

// Run the model; wait up to 20 s for the finished result in the same call
let res = await fetch(API + "/run/workflow-utilities/pick-image-by-index?wait=20", {
  method: "POST",
  headers,
  body: JSON.stringify({
    "image_urls": [
      "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
    ],
    "index": 1
  }),
});
let request = await res.json();
if (!res.ok) throw new Error(request.error.code + ": " + request.error.message);

// Not finished yet: long-poll until it is
while (request.status === "queued" || request.status === "running") {
  res = await fetch(API + "/requests/" + request.id + "?wait=20", { headers });
  request = await res.json();
}
if (request.status !== "succeeded") throw new Error(JSON.stringify(request.error));
console.log(request.outputs.map((o) => o.url), request.cost.credits + " API credits ($" + request.cost.usd + ")");
```

### Python

```python
import os
import requests

API = "https://api.doitong.com/v1"
headers = {"Authorization": "Bearer " + os.environ["DOITONG_API_KEY"]}

payload = {
    "image_urls": [
        "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg",
    ],
    "index": 1,
}

# Run the model; wait up to 20 s for the finished result in the same call
r = requests.post(API + "/run/workflow-utilities/pick-image-by-index", params={"wait": 20}, json=payload, headers=headers)
request = r.json()
if not r.ok:
    raise RuntimeError(request["error"]["code"] + ": " + request["error"]["message"])

# Not finished yet: long-poll until it is
while request["status"] in ("queued", "running"):
    request = requests.get(API + "/requests/" + request["id"], params={"wait": 20}, headers=headers).json()
if request["status"] != "succeeded":
    raise RuntimeError(request["error"])
print([o["url"] for o in request["outputs"]], request["cost"]["credits"], "API credits", "$" + request["cost"]["usd"])
```

### MCP

The MCP server at `https://api.doitong.com/v1/mcp` exposes the tools `search_models`, `get_model`, `quote`, `run`, `get_request`, `cancel_request`, `list_requests`, `create_upload` and `get_account`. A `run` call for this model:

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "run",
    "arguments": {
      "model_id": "workflow-utilities/pick-image-by-index",
      "input": {
        "image_urls": [
          "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
        ],
        "index": 1
      },
      "wait_seconds": 20
    }
  }
}
```

## Response

Every call returns a request object. `status` is one of `queued`, `running`, `succeeded`, `failed`, `canceled`. `outputs` lists the generated files with URLs on our storage (kept forever, or 7 days with `?storage=temporary`; `storage` says which); `output` is the model's own result object with the same URLs.

```json
{
  "id": "req_8k2m4q7x1z9c3v5b6n0p2r4t",
  "object": "request",
  "model": "workflow-utilities/pick-image-by-index",
  "status": "succeeded",
  "created_at": "2026-10-20T12:00:00Z",
  "started_at": "2026-10-20T12:00:02Z",
  "completed_at": "2026-10-20T12:00:09Z",
  "queue_position": null,
  "cost": {
    "credits": 1,
    "usd": "0.001",
    "charged": 1,
    "refunded": 0
  },
  "input": {
    "image_urls": [
      "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
    ],
    "index": 1
  },
  "output": {
    "image": {
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_name": "0-output.jpeg",
      "file_size": 1843200,
      "width": 1024,
      "height": 768
    },
    "images": [
      {
        "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
        "content_type": "image/jpeg",
        "file_name": "0-output.jpeg",
        "file_size": 1843200,
        "width": 1024,
        "height": 768
      }
    ]
  },
  "outputs": [
    {
      "type": "image",
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_size": 1843200,
      "width": 1024,
      "height": 768,
      "stored": true
    }
  ],
  "error": null,
  "metrics": {
    "inference_seconds": 6.8
  },
  "urls": {
    "self": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t",
    "cancel": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t/cancel"
  }
}
```

### Output fields (`output`)

| Field | Type | Description |
|---|---|---|
| `image` | object {url, content_type, file_name, file_size, width, height} | Hình ảnh được chọn tại vị trí đã chỉ định. |
| `images` | array of object {url, content_type, file_name, file_size, width, height} | Đầu ra tương thích cho các nút hạ nguồn cần tham chiếu `images`, như được cung cấp bởi merge và các tiện ích khác. Đầu ra chứa hình ảnh đã chọn trong mảng một phần tử, nên các nút đó không cần thay đổi. |

## Related models

- [Workflow Utilities Extract Nth Frame](https://doitong.com/developers/models/workflow-utilities/extract-nth-frame.md) (`workflow-utilities/extract-nth-frame`): $0.001 / second of processing time
- [Workflow Utilities Auto Subtitle](https://doitong.com/developers/models/workflow-utilities/auto-subtitle.md) (`workflow-utilities/auto-subtitle`): $0.03 / minute of input video
- [Workflow Utilities Blend Video](https://doitong.com/developers/models/workflow-utilities/blend-video.md) (`workflow-utilities/blend-video`): $0.001 / second of processing time
- [Workflow Utilities Interleave Video](https://doitong.com/developers/models/workflow-utilities/interleave-video.md) (`workflow-utilities/interleave-video`): $0.00017 / second of processing time
- [Workflow Utilities Reverse Video](https://doitong.com/developers/models/workflow-utilities/reverse-video.md) (`workflow-utilities/reverse-video`): $0.001 / second of processing time
- [Workflow Utilities Scale Video](https://doitong.com/developers/models/workflow-utilities/scale-video.md) (`workflow-utilities/scale-video`): $0.001 / second of processing time
- [Workflow Utilities Trim Video](https://doitong.com/developers/models/workflow-utilities/trim-video.md) (`workflow-utilities/trim-video`): $0.001 / second of processing time
- [Workflow Utilities Audio Compressor](https://doitong.com/developers/models/workflow-utilities/audio-compressor.md) (`workflow-utilities/audio-compressor`): $0.001 / second of processing time

## Links

- HTML page: https://doitong.com/developers/models/workflow-utilities/pick-image-by-index
- All models and guides for AI agents: https://doitong.com/developers/llms.txt
- OpenAPI 3.1 with this model's typed request body: https://doitong.com/developers/openapi.json?model=workflow-utilities/pick-image-by-index
- Errors: https://doitong.com/developers/docs/errors
- Model details as JSON: https://api.doitong.com/v1/models/workflow-utilities/pick-image-by-index