Image Generation

HPP Router supports image generation via OpenAI's gpt-image-1 model through an OpenAI-compatible endpoint.

POST https://router.hpp.io/v1/images/generations

Request

Wallet

Include both the payment rail header and your API key:

curl

curl -X POST https://router.hpp.io/v1/images/generations \
  -H "apikey: $HPPROUTER_API_KEY" \
  -H "X-Payment-Rail: wallet" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-image-1",
    "prompt": "A serene mountain landscape at sunset",
    "size": "1024x1024",
    "quality": "auto",
    "n": 1
  }'

Parameters

Parameter	Values	Default
model	gpt-image-1	required
prompt	string	required
size	1024x1024, 1024x1536, 1536x1024	1024x1024
quality	low, medium, high, auto	auto
n	1–4	1
background	string	—
output_format	string	—

Response

{
  "created": 1732700000,
  "data": [
    { "b64_json": "..." }
  ],
  "usage": {
    "input_tokens": 14,
    "output_tokens": 4160,
    "total_tokens": 4174
  }
}

The image is returned as base64 (b64_json). The usage block reports the token counts used for billing.

Pricing (token-based)

Image generation is billed per token, like chat. For openai/gpt-image-1:

• Input (text tokens): $5 per 1M tokens (0.000005 / token)
• Output (image tokens): $40 per 1M tokens (0.00004 / token)

Confirm live rates with GET /llm/v1/models.

Higher quality settings consume more output tokens — for example, auto can use roughly 15× the output tokens of low. Choose the lowest quality that meets your needs to control cost.

Wallet payments

All image generation requests require authentication with an API key.

• Quota (default): omit X-Payment-Rail and bill against prepaid credit when applicable.
• Wallet: include X-Payment-Rail: wallet. For billable image models, a missing payment signature returns 402 PAYMENT REQUIRED with a PAYMENT-REQUIRED challenge — sign and retry with PAYMENT-SIGNATURE (see Errors and Chat Completions — wallet).
• After a successful authorized request, usage is logged and wallet settlement proceeds on-chain. Settlement failures are distinct from the initial 402 challenge.