# PNG Buffer renderer

## When to use

Use `QRCodePNGRenderer` when Node.js-compatible code needs PNG bytes for a file, HTTP response,
attachment, object store, or another binary API.

## Minimal example

```ts
import {qrcode} from '@qrcodesdk/core';
import {QRCodePNGRenderer} from '@qrcodesdk/node';

const png = qrcode('https://qrcodesdk.dev').render(QRCodePNGRenderer());
```

## Return value

The renderer synchronously returns a Node.js `Buffer` containing a complete PNG file. Its pixel
width and height are `size × (matrix width + 2 × margin)`.

## Renderer-specific options

`QRCodePNGRendererOptions` accepts the
[shared visual options](/guides/customize/#shared-visual-options) plus:

| Option                  | Type            | Default               | Effect                                             |
| ----------------------- | --------------- | --------------------- | -------------------------------------------------- |
| `compressionLevel`      | integer `0`–`9` | `9`                   | Sets the PNG DEFLATE compression level             |
| `image.source`          | `Buffer`        | required with `image` | Supplies already-read PNG bytes for a center image |
| `image.size`            | `number`        | `0.4`                 | Image box as a fraction of matrix width            |
| `image.padding`         | `number`        | `1`                   | Clear padding measured in modules                  |
| `image.clearBackground` | `boolean`       | `true`                | Clears modules behind the image and padding        |

Compression changes encoding effort and file size, not the rendered QR modules. A level of `0`
disables DEFLATE compression; `9` requests the highest level.

## Renderer-specific constraints

- `compressionLevel` must be a safe integer from `0` through `9`.
- `image.source` must be a Node.js `Buffer` containing valid PNG bytes. Other formats, paths, and
  URLs are not decoded.
- Center images preserve aspect ratio, are composited with alpha, and are contained within the
  configured square without cropping.

## Related guides

- [Customize appearance](/guides/customize/) for shared styling and scan safety.
- [Add a center image](/guides/center-images/) for reading and sizing a PNG overlay.
- [Download or save](/guides/download-or-save/) for writing the `Buffer` to disk.
- [Serve a QR code](/guides/server-output/) for `image/png` HTTP responses.