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# kCGImageSourceThumbnailMaxPixelSize

The maximum width and height of a thumbnail image, specified in pixels.

```
let kCGImageSourceThumbnailMaxPixelSize: CFString
```

## Discussion

If this key is not specified, the width and height of a thumbnail is not limited and thumbnails may be as big as the image itself. If present, this key must be a CFNumber value. This key can be provided in the options dictionary that you pass to the function [`CGImageSourceCreateThumbnailAtIndex(_:_:_:)`](/documentation/ImageIO/CGImageSourceCreateThumbnailAtIndex(_:_:_:)).

---

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