# Image to image

> Send input images with a generation to edit or reference them. Input roles, which models accept them, uploading local files, and what inputs cost.

An edit is the same `POST /image/generate` as a text prompt, plus `inputs`.
Pass a model whose catalog entry lists `img->img`, and check its
`inputs.rules` for how many images it takes.

**SDK**

```ts
import Mynth from "@mynthio/sdk";

const mynth = new Mynth();

const task = await mynth.image.generate({
  model: "black-forest-labs/flux.2-pro",
  prompt: "The same lighthouse, now in heavy fog",
  inputs: ["https://cdn.example.com/lighthouse.png"],
});
```

**CLI**

```bash
npx @mynthio/cli image generate \
  -m black-forest-labs/flux.2-pro \
  -p "The same lighthouse, now in heavy fog" \
  -i https://cdn.example.com/lighthouse.png
```

**REST**

```bash
curl https://api.mynth.io/image/generate \
  -H "Authorization: Bearer $MYNTH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "black-forest-labs/flux.2-pro",
    "prompt": "The same lighthouse, now in heavy fog",
    "inputs": ["https://cdn.example.com/lighthouse.png"]
  }'
```

## Inputs and roles

`inputs` takes up to 20 entries. A string is a public image URL. The object
form sets a role:

```json
{
  "type": "image",
  "as": "reference",
  "source": { "type": "url", "url": "https://cdn.example.com/lighthouse.png" }
}
```

| `as`        | Meaning                                                |
| ----------- | ------------------------------------------------------ |
| `source`    | The image to edit                                      |
| `reference` | An image to take style or content from                 |
| `auto`      | Let Mynth assign a role the model accepts. The default |

The catalog entry's `inputs.rules` says which roles the model has and how many
images each allows. A rule with no `kind` accepts any image. In the CLI, set a
role with a prefix: `-i source:./photo.png` or `-i reference:https://...`.

An input URL must be reachable from the public internet. An image Mynth cannot
fetch or read fails with `INVALID_INPUT`.

## Pass a model that edits

With an explicit model, inputs are checked when the task is created. A model
that cannot take them, or too many of them, answers `400 VALIDATION_ERROR` and
nothing is queued.

`auto` does not look at `inputs`. An edit sent with `auto` can be accepted and
then fail with `CAPABILITY_NOT_SUPPORTED` when it lands on a model that cannot
edit. [The model field](https://mynth.io/docs/models.md#auto-is-experimental) has the details.

## Local files

The SDK and the CLI upload local files for you. In the SDK, put a `File` or
`Blob` in `inputs`. In the CLI, pass a path to `-i`.

```ts
const task = await mynth.image.generate({
  model: "black-forest-labs/flux.2-pro",
  prompt: "The same lighthouse, at noon",
  inputs: [file],
});
```

Over REST, upload first with `POST /image/upload` and pass the returned URLs:

```bash
curl https://api.mynth.io/image/upload \
  -H "Authorization: Bearer $MYNTH_API_KEY" \
  -F "images=@./lighthouse.png"
```

```json
{ "data": { "urls": ["https://cdn.mynth.io/inputs/img_3f9a0c1d2e4b5a6978c0d1e2f3a4b5c6.png"] } }
```

An upload takes up to 10 JPEG, PNG, or WEBP files, each between 1 KB and
10 MB. It is free, and the URLs are served for 1 day. The SDK and the CLI send
all local files of one request in a single upload, so the same 10-file limit
applies to them.

## Price

Models that charge for inputs list `perInput` in the catalog. It is charged
once per input image for each successful output, so two inputs at `count: 4`
add eight input charges to the four image charges. A model without `perInput`
charges nothing for inputs. [Pricing](https://mynth.io/docs/pricing.md#image-price) has the
formula.

## Next steps

- [Generate images](https://mynth.io/docs/guides/generate-images.md): the rest of the request.
- [Choosing an image model](https://mynth.io/docs/models/choosing.md): finding a model that edits.
- [Remove background](https://mynth.io/docs/guides/remove-background.md): a cutout without a prompt.