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sharp/docs/api-output.md
Lovell Fuller ec26c8aa49 Docs: ensure toBuffer pixel example works #2624
2021-03-21 20:54:09 +00:00

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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
## toFile
Write output image data to a file.
If an explicit output format is not selected, it will be inferred from the extension,
with JPEG, PNG, WebP, AVIF, TIFF, DZI, and libvips' V format supported.
Note that raw pixel data is only supported for buffer output.
By default all metadata will be removed, which includes EXIF-based orientation.
See [withMetadata][1] for control over this.
A `Promise` is returned when `callback` is not provided.
### Parameters
- `fileOut` **[string][2]** the path to write the image data to.
- `callback` **[Function][3]?** called on completion with two arguments `(err, info)`.
`info` contains the output image `format`, `size` (bytes), `width`, `height`,
`channels` and `premultiplied` (indicating if premultiplication was used).
When using a crop strategy also contains `cropOffsetLeft` and `cropOffsetTop`.
### Examples
```javascript
sharp(input)
.toFile('output.png', (err, info) => { ... });
```
```javascript
sharp(input)
.toFile('output.png')
.then(info => { ... })
.catch(err => { ... });
```
- Throws **[Error][4]** Invalid parameters
Returns **[Promise][5]&lt;[Object][6]>** when no callback is provided
## toBuffer
Write output to a Buffer.
JPEG, PNG, WebP, AVIF, TIFF and raw pixel data output are supported.
If no explicit format is set, the output format will match the input image, except GIF and SVG input which become PNG output.
By default all metadata will be removed, which includes EXIF-based orientation.
See [withMetadata][1] for control over this.
`callback`, if present, gets three arguments `(err, data, info)` where:
- `err` is an error, if any.
- `data` is the output image data.
- `info` contains the output image `format`, `size` (bytes), `width`, `height`,
`channels` and `premultiplied` (indicating if premultiplication was used).
When using a crop strategy also contains `cropOffsetLeft` and `cropOffsetTop`.
A `Promise` is returned when `callback` is not provided.
### Parameters
- `options` **[Object][6]?**
- `options.resolveWithObject` **[boolean][7]?** Resolve the Promise with an Object containing `data` and `info` properties instead of resolving only with `data`.
- `callback` **[Function][3]?**
### Examples
```javascript
sharp(input)
.toBuffer((err, data, info) => { ... });
```
```javascript
sharp(input)
.toBuffer()
.then(data => { ... })
.catch(err => { ... });
```
```javascript
sharp(input)
.toBuffer({ resolveWithObject: true })
.then(({ data, info }) => { ... })
.catch(err => { ... });
```
```javascript
const { data, info } = await sharp('my-image.jpg')
// output the raw pixels
.raw()
.toBuffer({ resolveWithObject: true });
// create a more type safe way to work with the raw pixel data
// this will not copy the data, instead it will change `data`s underlying ArrayBuffer
// so `data` and `pixelArray` point to the same memory location
const pixelArray = new Uint8ClampedArray(data.buffer);
// When you are done changing the pixelArray, sharp takes the `pixelArray` as an input
const { width, height, channels } = info;
await sharp(pixelArray, { raw: { width, height, channels } })
.toFile('my-changed-image.jpg');
```
Returns **[Promise][5]&lt;[Buffer][8]>** when no callback is provided
## withMetadata
Include all metadata (EXIF, XMP, IPTC) from the input image in the output image.
This will also convert to and add a web-friendly sRGB ICC profile unless a custom
output profile is provided.
The default behaviour, when `withMetadata` is not used, is to convert to the device-independent
sRGB colour space and strip all metadata, including the removal of any ICC profile.
### Parameters
- `options` **[Object][6]?**
- `options.orientation` **[number][9]?** value between 1 and 8, used to update the EXIF `Orientation` tag.
- `options.icc` **[string][2]?** filesystem path to output ICC profile, defaults to sRGB.
### Examples
```javascript
sharp('input.jpg')
.withMetadata()
.toFile('output-with-metadata.jpg')
.then(info => { ... });
```
- Throws **[Error][4]** Invalid parameters
Returns **Sharp**
## toFormat
Force output to a given format.
### Parameters
- `format` **([string][2] \| [Object][6])** as a string or an Object with an 'id' attribute
- `options` **[Object][6]** output options
### Examples
```javascript
// Convert any input to PNG output
const data = await sharp(input)
.toFormat('png')
.toBuffer();
```
- Throws **[Error][4]** unsupported format or options
Returns **Sharp**
## jpeg
Use these JPEG options for output image.
### Parameters
- `options` **[Object][6]?** output options
- `options.quality` **[number][9]** quality, integer 1-100 (optional, default `80`)
- `options.progressive` **[boolean][7]** use progressive (interlace) scan (optional, default `false`)
- `options.chromaSubsampling` **[string][2]** set to '4:4:4' to prevent chroma subsampling otherwise defaults to '4:2:0' chroma subsampling (optional, default `'4:2:0'`)
- `options.optimiseCoding` **[boolean][7]** optimise Huffman coding tables (optional, default `true`)
- `options.optimizeCoding` **[boolean][7]** alternative spelling of optimiseCoding (optional, default `true`)
- `options.mozjpeg` **[boolean][7]** use mozjpeg defaults, equivalent to `{ trellisQuantisation: true, overshootDeringing: true, optimiseScans: true, quantisationTable: 3 }` (optional, default `false`)
- `options.trellisQuantisation` **[boolean][7]** apply trellis quantisation (optional, default `false`)
- `options.overshootDeringing` **[boolean][7]** apply overshoot deringing (optional, default `false`)
- `options.optimiseScans` **[boolean][7]** optimise progressive scans, forces progressive (optional, default `false`)
- `options.optimizeScans` **[boolean][7]** alternative spelling of optimiseScans (optional, default `false`)
- `options.quantisationTable` **[number][9]** quantization table to use, integer 0-8 (optional, default `0`)
- `options.quantizationTable` **[number][9]** alternative spelling of quantisationTable (optional, default `0`)
- `options.force` **[boolean][7]** force JPEG output, otherwise attempt to use input format (optional, default `true`)
### Examples
```javascript
// Convert any input to very high quality JPEG output
const data = await sharp(input)
.jpeg({
quality: 100,
chromaSubsampling: '4:4:4'
})
.toBuffer();
```
```javascript
// Use mozjpeg to reduce output JPEG file size (slower)
const data = await sharp(input)
.jpeg({ mozjpeg: true })
.toBuffer();
```
- Throws **[Error][4]** Invalid options
Returns **Sharp**
## png
Use these PNG options for output image.
By default, PNG output is full colour at 8 or 16 bits per pixel.
Indexed PNG input at 1, 2 or 4 bits per pixel is converted to 8 bits per pixel.
Set `palette` to `true` for slower, indexed PNG output.
### Parameters
- `options` **[Object][6]?**
- `options.progressive` **[boolean][7]** use progressive (interlace) scan (optional, default `false`)
- `options.compressionLevel` **[number][9]** zlib compression level, 0 (fastest, largest) to 9 (slowest, smallest) (optional, default `6`)
- `options.adaptiveFiltering` **[boolean][7]** use adaptive row filtering (optional, default `false`)
- `options.palette` **[boolean][7]** quantise to a palette-based image with alpha transparency support (optional, default `false`)
- `options.quality` **[number][9]** use the lowest number of colours needed to achieve given quality, sets `palette` to `true` (optional, default `100`)
- `options.colours` **[number][9]** maximum number of palette entries, sets `palette` to `true` (optional, default `256`)
- `options.colors` **[number][9]** alternative spelling of `options.colours`, sets `palette` to `true` (optional, default `256`)
- `options.dither` **[number][9]** level of Floyd-Steinberg error diffusion, sets `palette` to `true` (optional, default `1.0`)
- `options.force` **[boolean][7]** force PNG output, otherwise attempt to use input format (optional, default `true`)
### Examples
```javascript
// Convert any input to full colour PNG output
const data = await sharp(input)
.png()
.toBuffer();
```
```javascript
// Convert any input to indexed PNG output (slower)
const data = await sharp(input)
.png({ palette: true })
.toBuffer();
```
- Throws **[Error][4]** Invalid options
Returns **Sharp**
## webp
Use these WebP options for output image.
### Parameters
- `options` **[Object][6]?** output options
- `options.quality` **[number][9]** quality, integer 1-100 (optional, default `80`)
- `options.alphaQuality` **[number][9]** quality of alpha layer, integer 0-100 (optional, default `100`)
- `options.lossless` **[boolean][7]** use lossless compression mode (optional, default `false`)
- `options.nearLossless` **[boolean][7]** use near_lossless compression mode (optional, default `false`)
- `options.smartSubsample` **[boolean][7]** use high quality chroma subsampling (optional, default `false`)
- `options.reductionEffort` **[number][9]** level of CPU effort to reduce file size, integer 0-6 (optional, default `4`)
- `options.pageHeight` **[number][9]?** page height for animated output
- `options.loop` **[number][9]** number of animation iterations, use 0 for infinite animation (optional, default `0`)
- `options.delay` **[Array][10]&lt;[number][9]>?** list of delays between animation frames (in milliseconds)
- `options.force` **[boolean][7]** force WebP output, otherwise attempt to use input format (optional, default `true`)
### Examples
```javascript
// Convert any input to lossless WebP output
const data = await sharp(input)
.webp({ lossless: true })
.toBuffer();
```
- Throws **[Error][4]** Invalid options
Returns **Sharp**
## gif
Use these GIF options for output image.
Requires libvips compiled with support for ImageMagick or GraphicsMagick.
The prebuilt binaries do not include this - see
[installing a custom libvips][11].
### Parameters
- `options` **[Object][6]?** output options
- `options.pageHeight` **[number][9]?** page height for animated output
- `options.loop` **[number][9]** number of animation iterations, use 0 for infinite animation (optional, default `0`)
- `options.delay` **[Array][10]&lt;[number][9]>?** list of delays between animation frames (in milliseconds)
- `options.force` **[boolean][7]** force GIF output, otherwise attempt to use input format (optional, default `true`)
- Throws **[Error][4]** Invalid options
Returns **Sharp**
## tiff
Use these TIFF options for output image.
### Parameters
- `options` **[Object][6]?** output options
- `options.quality` **[number][9]** quality, integer 1-100 (optional, default `80`)
- `options.force` **[boolean][7]** force TIFF output, otherwise attempt to use input format (optional, default `true`)
- `options.compression` **[string][2]** compression options: lzw, deflate, jpeg, ccittfax4 (optional, default `'jpeg'`)
- `options.predictor` **[string][2]** compression predictor options: none, horizontal, float (optional, default `'horizontal'`)
- `options.pyramid` **[boolean][7]** write an image pyramid (optional, default `false`)
- `options.tile` **[boolean][7]** write a tiled tiff (optional, default `false`)
- `options.tileWidth` **[number][9]** horizontal tile size (optional, default `256`)
- `options.tileHeight` **[number][9]** vertical tile size (optional, default `256`)
- `options.xres` **[number][9]** horizontal resolution in pixels/mm (optional, default `1.0`)
- `options.yres` **[number][9]** vertical resolution in pixels/mm (optional, default `1.0`)
- `options.bitdepth` **[number][9]** reduce bitdepth to 1, 2 or 4 bit (optional, default `8`)
### Examples
```javascript
// Convert SVG input to LZW-compressed, 1 bit per pixel TIFF output
sharp('input.svg')
.tiff({
compression: 'lzw',
bitdepth: 1
})
.toFile('1-bpp-output.tiff')
.then(info => { ... });
```
- Throws **[Error][4]** Invalid options
Returns **Sharp**
## avif
Use these AVIF options for output image.
Whilst it is possible to create AVIF images smaller than 16x16 pixels,
most web browsers do not display these properly.
### Parameters
- `options` **[Object][6]?** output options
- `options.quality` **[number][9]** quality, integer 1-100 (optional, default `50`)
- `options.lossless` **[boolean][7]** use lossless compression (optional, default `false`)
- `options.speed` **[number][9]** CPU effort vs file size, 0 (slowest/smallest) to 8 (fastest/largest) (optional, default `5`)
- `options.chromaSubsampling` **[string][2]** set to '4:4:4' to prevent chroma subsampling otherwise defaults to '4:2:0' chroma subsampling, requires libvips v8.11.0 (optional, default `'4:2:0'`)
- Throws **[Error][4]** Invalid options
Returns **Sharp**
**Meta**
- **since**: 0.27.0
## heif
Use these HEIF options for output image.
Support for patent-encumbered HEIC images requires the use of a
globally-installed libvips compiled with support for libheif, libde265 and x265.
### Parameters
- `options` **[Object][6]?** output options
- `options.quality` **[number][9]** quality, integer 1-100 (optional, default `50`)
- `options.compression` **[string][2]** compression format: av1, hevc (optional, default `'av1'`)
- `options.lossless` **[boolean][7]** use lossless compression (optional, default `false`)
- `options.speed` **[number][9]** CPU effort vs file size, 0 (slowest/smallest) to 8 (fastest/largest) (optional, default `5`)
- `options.chromaSubsampling` **[string][2]** set to '4:4:4' to prevent chroma subsampling otherwise defaults to '4:2:0' chroma subsampling, requires libvips v8.11.0 (optional, default `'4:2:0'`)
- Throws **[Error][4]** Invalid options
Returns **Sharp**
**Meta**
- **since**: 0.23.0
## raw
Force output to be raw, uncompressed, 8-bit unsigned integer (unit8) pixel data.
Pixel ordering is left-to-right, top-to-bottom, without padding.
Channel ordering will be RGB or RGBA for non-greyscale colourspaces.
### Examples
```javascript
// Extract raw RGB pixel data from JPEG input
const { data, info } = await sharp('input.jpg')
.raw()
.toBuffer({ resolveWithObject: true });
```
```javascript
// Extract alpha channel as raw pixel data from PNG input
const data = await sharp('input.png')
.ensureAlpha()
.extractChannel(3)
.toColourspace('b-w')
.raw()
.toBuffer();
```
Returns **Sharp**
## tile
Use tile-based deep zoom (image pyramid) output.
Set the format and options for tile images via the `toFormat`, `jpeg`, `png` or `webp` functions.
Use a `.zip` or `.szi` file extension with `toFile` to write to a compressed archive file format.
Warning: multiple sharp instances concurrently producing tile output can expose a possible race condition in some versions of libgsf.
### Parameters
- `options` **[Object][6]?**
- `options.size` **[number][9]** tile size in pixels, a value between 1 and 8192. (optional, default `256`)
- `options.overlap` **[number][9]** tile overlap in pixels, a value between 0 and 8192. (optional, default `0`)
- `options.angle` **[number][9]** tile angle of rotation, must be a multiple of 90. (optional, default `0`)
- `options.background` **([string][2] \| [Object][6])** background colour, parsed by the [color][12] module, defaults to white without transparency. (optional, default `{r:255,g:255,b:255,alpha:1}`)
- `options.depth` **[string][2]?** how deep to make the pyramid, possible values are `onepixel`, `onetile` or `one`, default based on layout.
- `options.skipBlanks` **[number][9]** threshold to skip tile generation, a value 0 - 255 for 8-bit images or 0 - 65535 for 16-bit images (optional, default `-1`)
- `options.container` **[string][2]** tile container, with value `fs` (filesystem) or `zip` (compressed file). (optional, default `'fs'`)
- `options.layout` **[string][2]** filesystem layout, possible values are `dz`, `iiif`, `zoomify` or `google`. (optional, default `'dz'`)
- `options.centre` **[boolean][7]** centre image in tile. (optional, default `false`)
- `options.center` **[boolean][7]** alternative spelling of centre. (optional, default `false`)
- `options.id` **[string][2]** when `layout` is `iiif`, sets the `@id` attribute of `info.json` (optional, default `'https://example.com/iiif'`)
### Examples
```javascript
sharp('input.tiff')
.png()
.tile({
size: 512
})
.toFile('output.dz', function(err, info) {
// output.dzi is the Deep Zoom XML definition
// output_files contains 512x512 tiles grouped by zoom level
});
```
- Throws **[Error][4]** Invalid parameters
Returns **Sharp**
[1]: #withmetadata
[2]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String
[3]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function
[4]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Error
[5]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Promise
[6]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object
[7]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean
[8]: https://nodejs.org/api/buffer.html
[9]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number
[10]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array
[11]: https://sharp.pixelplumbing.com/install#custom-libvips
[12]: https://www.npmjs.org/package/color
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