# How to Specify Platform-Specific Requirements for Image Generation in GPT-Image-2

> Specify platform-specific image generation requirements for GPT-Image-2 by customizing size quality and format parameters in generateImage function before Vercel deployment

- Repository: [苍何/awesome-gpt-image-2](https://github.com/freestylefly/awesome-gpt-image-2)
- Tags: how-to-guide
- Published: 2026-08-28

---

**You specify platform-specific requirements for image generation by modifying the `size`, `quality`, and `format` parameters in the `generateImage()` function inside [`api/generate-image.js`](https://github.com/freestylefly/awesome-gpt-image-2/blob/main/api/generate-image.js) before deploying to Vercel.**

The **freestylefly/awesome-gpt-image-2** repository provides a Vercel serverless function that proxies requests to the GPT-Image-2 API. Understanding how to specify platform-specific requirements for image generation allows you to tailor output resolution, compression, and file format to match the constraints of web dashboards, mobile applications, or print media.

## Understanding the Image Generation Flow

Image generation is handled by the Vercel serverless function located at [`api/generate-image.js`](https://github.com/freestylefly/awesome-gpt-image-2/blob/main/api/generate-image.js). Inside this file, the `generateImage()` helper function (defined at lines 27-42) constructs the payload sent to the upstream GPT-Image-2 service.

The request body contains three critical fields that control the **platform-specific requirements**:

```javascript
body: JSON.stringify({
  model: 'gpt-image-2',
  prompt,
  n: 1,
  size: '1024x1024',   // ← resolution
  quality: 'low',      // ← compression quality
  format: 'jpeg'       // ← output format
})

```

These values are currently hard-coded in the source code, meaning every image generation request uses the same specifications unless you modify the function.

## Platform-Specific Parameters Explained

### Image Resolution (size)

The **size** parameter defines the output dimensions as a string in `WIDTHxHEIGHT` format. The default value is `'1024x1024'`.

- Use `'1024x1024'` for standard web content
- Use `'512x512'` for thumbnails or mobile-optimized assets
- Use `'1792x1024'` or wide aspect ratios for banner images

### Compression Quality (quality)

The **quality** parameter controls the compression level and file size. Valid values are `'low'`, `'medium'`, and `'high'`.

- **low**: Fastest generation, smallest file size, artifacting present (default)
- **medium**: Balanced quality for most web applications
- **high**: Maximum fidelity for print or editorial platforms

### Output Format (format)

The **format** parameter determines the file encoding. Supported values include `'jpeg'`, `'png'`, and `'webp'`.

- **jpeg**: Best for photographs, smallest file size (default)
- **png**: Lossless compression required for editing workflows or transparency
- **webp**: Modern web format for bandwidth-constrained platforms

## Modifying Platform-Specific Requirements

### Method 1: Hardcode Values for Static Requirements

For applications where all generated images share the same specifications, edit the payload directly in [`api/generate-image.js`](https://github.com/freestylefly/awesome-gpt-image-2/blob/main/api/generate-image.js):

1. Open [`api/generate-image.js`](https://github.com/freestylefly/awesome-gpt-image-2/blob/main/api/generate-image.js) and locate the `generateImage()` function
2. Modify the `size`, `quality`, or `format` values to match your target platform

Example for a high-resolution PNG suitable for design tools:

```javascript
body: JSON.stringify({
  model: 'gpt-image-2',
  prompt,
  n: 1,
  size: '1792x1024',
  quality: 'high',
  format: 'png'
})

```

### Method 2: Expose Parameters via API Request

To allow dynamic platform-specific requirements per request, refactor the function to accept an options object. First, update the request handler to parse incoming parameters:

```javascript
// In api/generate-image.js request handler
const { prompt, caseId, size = '1024x1024', quality = 'low', format = 'jpeg' } = body;

```

Then pass these values to the generation function:

```javascript
const image = await generateImage(prompt, { size, quality, format });

```

Finally, update `generateImage()` to accept and utilize the options object when constructing the upstream payload.

## Deployment Considerations

Since the generation logic runs as a Vercel serverless function, changes to [`api/generate-image.js`](https://github.com/freestylefly/awesome-gpt-image-2/blob/main/api/generate-image.js) require a new deployment. Push your modifications to the `main` branch or trigger a manual redeploy through the Vercel dashboard.

Note that environment variables defined in `.env.example` (such as `CIYUAN_API_KEY` and `CIYUAN_BASE_URL`) configure authentication and routing only. These variables do **not** affect the image-specific generation parameters, which must be modified in the source code itself.

## Summary

- **Platform-specific requirements** in GPT-Image-2 are controlled by three fields: `size`, `quality`, and `format` in [`api/generate-image.js`](https://github.com/freestylefly/awesome-gpt-image-2/blob/main/api/generate-image.js)
- Default values are `'1024x1024'` resolution, `'low'` quality, and `'jpeg'` format
- Modify the hard-coded values in the `generateImage()` function for static requirements
- Refactor to accept request body parameters for dynamic, caller-defined specifications
- Any code changes require redeployment to Vercel to take effect
- Environment variables only handle API keys and URLs, not image generation parameters

## Frequently Asked Questions

### How do I generate images for mobile apps with smaller file sizes?

Set the **size** parameter to `'512x512'` and keep **quality** at `'low'` in the [`api/generate-image.js`](https://github.com/freestylefly/awesome-gpt-image-2/blob/main/api/generate-image.js) payload. This reduces both dimensions and compression artifacts while maintaining acceptable visual quality for mobile screens. You can also switch the **format** to `'webp'` for additional bandwidth savings on modern mobile platforms.

### Can I change image specifications without redeploying the code?

No. Because the `size`, `quality`, and `format` values are hard-coded in [`api/generate-image.js`](https://github.com/freestylefly/awesome-gpt-image-2/blob/main/api/generate-image.js) according to the current implementation, any modification to these platform-specific requirements requires editing the source file and redeploying the Vercel function. To avoid redeployment, refactor the code to read these values from the request body or environment variables.

### What file formats are supported for platform-specific image generation?

According to the source code in `freestylefly/awesome-gpt-image-2`, the API accepts `'jpeg'`, `'png'`, and `'webp'` for the **format** field. JPEG is the default and works best for photographic content, while PNG provides lossless quality necessary for graphic design workflows. WebP offers superior compression for web platforms.

### Where are the image generation settings configured if not in .env files?

The image generation settings are hard-coded in the `generateImage()` function within [`api/generate-image.js`](https://github.com/freestylefly/awesome-gpt-image-2/blob/main/api/generate-image.js) (lines 27-42). The `.env.example` file only contains environment variables for `CIYUAN_API_KEY` and `CIYUAN_BASE_URL`, which handle authentication and API routing, not the visual specifications of the generated images.