AI cake design preview for a bakery order: photo reference and mask

To preview a cake design, photograph your plain base cake, pass it as an input_reference to openai/gpt-image-2.5, and describe only the decoration. Add mask_url when you want the change confined to the top or one tier. Request three or four takes with n so the customer can pick.

The preview is an illustration of intent, not a promise: tell the customer the baker's piping will differ, and keep the order wording, date and price in your order system, not in the image.

What goes where

The request

The prompt names what changes and what stays. Say which tier, which colours, and that the plate, table and lighting remain.

{
  "model": "openai/gpt-image-2.5",
  "prompt": "Decorate the top tier only with pale pink buttercream roses and a gold number 7 topper. Keep the cake shape, the plate, the table and the lighting unchanged.",
  "input_references": [
    {"type": "image_url", "image_url": {"url": "https://example.com/base-cake.jpg"}}
  ],
  "mask_url": "https://example.com/top-tier-mask.png",
  "n": 3
}

Order summary in code

Keep the order text outside the model. This builds the line your bakery sheet prints, so a spelling mistake in a name never comes from image generation.

order = {"name": "Maya", "age": 7, "flavour": "vanilla", "collect": "2026-10-18"}
line = f"{order['name']} turns {order['age']}: {order['flavour']} cake, collect {order['collect']}"
print(line)

Limits to say out loud

Ask for edible-looking decoration you can really make. A model will happily draw floating sugar that no baker can build, so choose the winning take with your baker, not just the customer.