sharp/docs/api-composite.md

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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
### Table of Contents
- [overlayWith][1]
## overlayWith
Overlay (composite) an image over the processed (resized, extracted etc.) image.
The overlay image must be the same size or smaller than the processed image.
If both `top` and `left` options are provided, they take precedence over `gravity`.
If the overlay image contains an alpha channel then composition with premultiplication will occur.
**Parameters**
- `overlay` **([Buffer][2] \| [String][3])** Buffer containing image data or String containing the path to an image file.
- `options` **[Object][4]?**
- `options.gravity` **[String][3]** gravity at which to place the overlay. (optional, default `'centre'`)
- `options.top` **[Number][5]?** the pixel offset from the top edge.
- `options.left` **[Number][5]?** the pixel offset from the left edge.
- `options.tile` **[Boolean][6]** set to true to repeat the overlay image across the entire image with the given `gravity`. (optional, default `false`)
- `options.cutout` **[Boolean][6]** set to true to apply only the alpha channel of the overlay image to the input image, giving the appearance of one image being cut out of another. (optional, default `false`)
- `options.density` **[Number][5]** integral number representing the DPI for vector overlay image. (optional, default `72`)
- `options.raw` **[Object][4]?** describes overlay when using raw pixel data.
- `options.raw.width` **[Number][5]?**
- `options.raw.height` **[Number][5]?**
- `options.raw.channels` **[Number][5]?**
- `options.create` **[Object][4]?** describes a blank overlay to be created.
- `options.create.width` **[Number][5]?**
- `options.create.height` **[Number][5]?**
- `options.create.channels` **[Number][5]?** 3-4
- `options.create.background` **([String][3] \| [Object][4])?** parsed by the [color][7] module to extract values for red, green, blue and alpha.
**Examples**
```javascript
sharp('input.png')
.rotate(180)
.resize(300)
.flatten()
.background('#ff6600')
.overlayWith('overlay.png', { gravity: sharp.gravity.southeast } )
.sharpen()
.withMetadata()
.quality(90)
.webp()
.toBuffer()
.then(function(outputBuffer) {
// outputBuffer contains upside down, 300px wide, alpha channel flattened
// onto orange background, composited with overlay.png with SE gravity,
// sharpened, with metadata, 90% quality WebP image data. Phew!
});
```
- Throws **[Error][8]** Invalid parameters
Returns **Sharp**
[1]: #overlaywith
[2]: https://nodejs.org/api/buffer.html
[3]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String
[4]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object
[5]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number
[6]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean
[7]: https://www.npmjs.org/package/color
[8]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Error