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Modularise JS source in 'lib' subdirectory.

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Generate public API documention via jsdoc comments.
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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
# extractChannel
Extract a single channel from a multi-channel image.
**Parameters**
- `channel` **([Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number) \| [String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String))** zero-indexed band number to extract, or `red`, `green` or `blue` as alternative to `0`, `1` or `2` respectively.
**Examples**
```javascript
sharp(input)
.extractChannel('green')
.toFile('input_green.jpg', function(err, info) {
// info.channels === 1
// input_green.jpg contains the green channel of the input image
});
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid channel
Returns **Sharp**
# joinChannel
Join one or more channels to the image.
The meaning of the added channels depends on the output colourspace, set with `toColourspace()`.
By default the output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.
Channel ordering follows vips convention:
- sRGB: 0: Red, 1: Green, 2: Blue, 3: Alpha.
- CMYK: 0: Magenta, 1: Cyan, 2: Yellow, 3: Black, 4: Alpha.
Buffers may be any of the image formats supported by sharp: JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data.
For raw pixel input, the `options` object should contain a `raw` attribute, which follows the format of the attribute of the same name in the `sharp()` constructor.
**Parameters**
- `images` **([Array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array) \| [String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String) \| [Buffer](https://nodejs.org/api/buffer.html))** one or more images (file paths, Buffers).
- `Object` image options, see `sharp()` constructor.
- `options`
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# bandbool
Perform a bitwise boolean operation on all input image channels (bands) to produce a single channel output image.
**Parameters**
- `boolOp` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** one of `and`, `or` or `eor` to perform that bitwise operation, like the C logic operators `&`, `|` and `^` respectively.
**Examples**
```javascript
sharp('3-channel-rgb-input.png')
.bandbool(sharp.bool.and)
.toFile('1-channel-output.png', function (err, info) {
// The output will be a single channel image where each pixel `P = R & G & B`.
// If `I(1,1) = [247, 170, 14] = [0b11110111, 0b10101010, 0b00001111]`
// then `O(1,1) = 0b11110111 & 0b10101010 & 0b00001111 = 0b00000010 = 2`.
});
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**

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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
# background
Set the background for the `embed`, `flatten` and `extend` operations.
The default background is `{r: 0, g: 0, b: 0, a: 1}`, black without transparency.
Delegates to the _color_ module, which can throw an Error
but is liberal in what it accepts, clipping values to sensible min/max.
The alpha value is a float between `0` (transparent) and `1` (opaque).
**Parameters**
- `rgba` **([String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String) \| [Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object))** parsed by the [color](https://www.npmjs.org/package/color) module to extract values for red, green, blue and alpha.
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameter
Returns **Sharp**
# greyscale
Convert to 8-bit greyscale; 256 shades of grey.
This is a linear operation. If the input image is in a non-linear colour space such as sRGB, use `gamma()` with `greyscale()` for the best results.
By default the output image will be web-friendly sRGB and contain three (identical) color channels.
This may be overridden by other sharp operations such as `toColourspace('b-w')`,
which will produce an output image containing one color channel.
An alpha channel may be present, and will be unchanged by the operation.
**Parameters**
- `greyscale` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**
# grayscale
Alternative spelling of `greyscale`.
**Parameters**
- `grayscale` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**
# toColourspace
Set the output colourspace.
By default output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.
**Parameters**
- `colourspace` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** output colourspace e.g. `srgb`, `rgb`, `cmyk`, `lab`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L568)
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# toColorspace
Alternative spelling of `toColourspace`.
**Parameters**
- `colorspace` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** output colorspace.
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**

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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
# 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`.
**Parameters**
- `overlay` **([Buffer](https://nodejs.org/api/buffer.html) \| [String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String))** Buffer containing image data or String containing the path to an image file.
- `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]**
- `options.gravity` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** gravity at which to place the overlay. (optional, default `'centre'`)
- `options.top` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the pixel offset from the top edge.
- `options.left` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the pixel offset from the left edge.
- `options.tile` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** set to true to repeat the overlay image across the entire image with the given `gravity`. (optional, default `false`)
- `options.cutout` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** 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.raw` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** describes overlay when using raw pixel data.
- `options.raw.width` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- `options.raw.height` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- `options.raw.channels` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
**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](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**

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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
#
**Parameters**
- `input` **\[([Buffer](https://nodejs.org/api/buffer.html) \| [String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String))]** if present, can be
a Buffer containing JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data, or
a String containing the path to an JPEG, PNG, WebP, GIF, SVG or TIFF image file.
JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data can be streamed into the object when null or undefined.
- `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** if present, is an Object with optional attributes.
- `options.density` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** integral number representing the DPI for vector images. (optional, default `72`)
- `options.raw` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** describes raw pixel image data. See `raw()` for pixel ordering.
- `options.raw.width` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- `options.raw.height` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- `options.raw.channels` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
**Examples**
```javascript
sharp('input.jpg')
.resize(300, 200)
.toFile('output.jpg', function(err) {
// output.jpg is a 300 pixels wide and 200 pixels high image
// containing a scaled and cropped version of input.jpg
});
```
```javascript
// Read image data from readableStream,
// resize to 300 pixels wide,
// emit an 'info' event with calculated dimensions
// and finally write image data to writableStream
var transformer = sharp()
.resize(300)
.on('info', function(info) {
console.log('Image height is ' + info.height);
});
readableStream.pipe(transformer).pipe(writableStream);
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# queue
An EventEmitter that emits a `change` event when a task is either:
- queued, waiting for _libuv_ to provide a worker thread
- complete
**Examples**
```javascript
sharp.queue.on('change', function(queueLength) {
console.log('Queue contains ' + queueLength + ' task(s)');
});
```
# format
An Object containing nested boolean values representing the available input and output formats/methods.
**Examples**
```javascript
console.log(sharp.format());
```
Returns **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)**
# versions
An Object containing the version numbers of libvips and its dependencies.
**Examples**
```javascript
console.log(sharp.versions);
```

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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
# clone
Take a "snapshot" of the Sharp instance, returning a new instance.
Cloned instances inherit the input of their parent instance.
This allows multiple output Streams and therefore multiple processing pipelines to share a single input Stream.
**Examples**
```javascript
const pipeline = sharp().rotate();
pipeline.clone().resize(800, 600).pipe(firstWritableStream);
pipeline.clone().extract({ left: 20, top: 20, width: 100, height: 100 }).pipe(secondWritableStream);
readableStream.pipe(pipeline);
// firstWritableStream receives auto-rotated, resized readableStream
// secondWritableStream receives auto-rotated, extracted region of readableStream
```
Returns **Sharp**
# metadata
Fast access to image metadata without decoding any compressed image data.
A Promises/A+ promise is returned when `callback` is not provided.
- `format`: Name of decoder used to decompress image data e.g. `jpeg`, `png`, `webp`, `gif`, `svg`
- `width`: Number of pixels wide
- `height`: Number of pixels high
- `space`: Name of colour space interpretation e.g. `srgb`, `rgb`, `cmyk`, `lab`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L568)
- `channels`: Number of bands e.g. `3` for sRGB, `4` for CMYK
- `density`: Number of pixels per inch (DPI), if present
- `hasProfile`: Boolean indicating the presence of an embedded ICC profile
- `hasAlpha`: Boolean indicating the presence of an alpha transparency channel
- `orientation`: Number value of the EXIF Orientation header, if present
- `exif`: Buffer containing raw EXIF data, if present
- `icc`: Buffer containing raw [ICC](https://www.npmjs.com/package/icc) profile data, if present
**Parameters**
- `callback` **\[[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)]** called with the arguments `(err, metadata)`
**Examples**
```javascript
const image = sharp(inputJpg);
image
.metadata()
.then(function(metadata) {
return image
.resize(Math.round(metadata.width / 2))
.webp()
.toBuffer();
})
.then(function(data) {
// data contains a WebP image half the width and height of the original JPEG
});
```
Returns **([Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) | Sharp)**
# limitInputPixels
Do not process input images where the number of pixels (width _ height) exceeds this limit.
Assumes image dimensions contained in the input metadata can be trusted.
The default limit is 268402689 (0x3FFF _ 0x3FFF) pixels.
**Parameters**
- `limit` **([Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number) \| [Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean))** an integral Number of pixels, zero or false to remove limit, true to use default limit.
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid limit
Returns **Sharp**
# sequentialRead
An advanced setting that switches the libvips access method to `VIPS_ACCESS_SEQUENTIAL`.
This will reduce memory usage and can improve performance on some systems.
**Parameters**
- `sequentialRead` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**

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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
# rotate
Rotate the output image by either an explicit angle
or auto-orient based on the EXIF `Orientation` tag.
Use this method without angle to determine the angle from EXIF data.
Mirroring is supported and may infer the use of a flip operation.
The use of `rotate` implies the removal of the EXIF `Orientation` tag, if any.
Method order is important when both rotating and extracting regions,
for example `rotate(x).extract(y)` will produce a different result to `extract(y).rotate(x)`.
**Parameters**
- `angle` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 0, 90, 180 or 270. (optional, default `auto`)
**Examples**
```javascript
const pipeline = sharp()
.rotate()
.resize(null, 200)
.toBuffer(function (err, outputBuffer, info) {
// outputBuffer contains 200px high JPEG image data,
// auto-rotated using EXIF Orientation tag
// info.width and info.height contain the dimensions of the resized image
});
readableStream.pipe(pipeline);
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# extract
Extract a region of the image.
- Use `extract` before `resize` for pre-resize extraction.
- Use `extract` after `resize` for post-resize extraction.
- Use `extract` before and after for both.
**Parameters**
- `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)**
- `options.left` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** zero-indexed offset from left edge
- `options.top` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** zero-indexed offset from top edge
- `options.width` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** dimension of extracted image
- `options.height` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** dimension of extracted image
**Examples**
```javascript
sharp(input)
.extract({ left: left, top: top, width: width, height: height })
.toFile(output, function(err) {
// Extract a region of the input image, saving in the same format.
});
```
```javascript
sharp(input)
.extract({ left: leftOffsetPre, top: topOffsetPre, width: widthPre, height: heightPre })
.resize(width, height)
.extract({ left: leftOffsetPost, top: topOffsetPost, width: widthPost, height: heightPost })
.toFile(output, function(err) {
// Extract a region, resize, then extract from the resized image
});
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# flip
Flip the image about the vertical Y axis. This always occurs after rotation, if any.
The use of `flip` implies the removal of the EXIF `Orientation` tag, if any.
**Parameters**
- `flip` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**
# flop
Flop the image about the horizontal X axis. This always occurs after rotation, if any.
The use of `flop` implies the removal of the EXIF `Orientation` tag, if any.
**Parameters**
- `flop` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**
# sharpen
Sharpen the image.
When used without parameters, performs a fast, mild sharpen of the output image.
When a `sigma` is provided, performs a slower, more accurate sharpen of the L channel in the LAB colour space.
Separate control over the level of sharpening in "flat" and "jagged" areas is available.
**Parameters**
- `sigma` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
- `flat` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the level of sharpening to apply to "flat" areas. (optional, default `1.0`)
- `jagged` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the level of sharpening to apply to "jagged" areas. (optional, default `2.0`)
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# blur
Blur the image.
When used without parameters, performs a fast, mild blur of the output image.
When a `sigma` is provided, performs a slower, more accurate Gaussian blur.
**Parameters**
- `sigma` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# extend
Extends/pads the edges of the image with the colour provided to the `background` method.
This operation will always occur after resizing and extraction, if any.
**Parameters**
- `extend` **([Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number) \| [Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object))** single pixel count to add to all edges or an Object with per-edge counts
- `extend.top` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- `extend.left` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- `extend.bottom` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- `extend.right` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
**Examples**
```javascript
// Resize to 140 pixels wide, then add 10 transparent pixels
// to the top, left and right edges and 20 to the bottom edge
sharp(input)
.resize(140)
.background({r: 0, g: 0, b: 0, a: 0})
.extend({top: 10, bottom: 20, left: 10, right: 10})
...
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# flatten
Merge alpha transparency channel, if any, with `background`.
**Parameters**
- `flatten` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**
# trim
Trim "boring" pixels from all edges that contain values within a percentage similarity of the top-left pixel.
**Parameters**
- `tolerance` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** value between 1 and 99 representing the percentage similarity. (optional, default `10`)
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# gamma
Apply a gamma correction by reducing the encoding (darken) pre-resize at a factor of `1/gamma`
then increasing the encoding (brighten) post-resize at a factor of `gamma`.
This can improve the perceived brightness of a resized image in non-linear colour spaces.
JPEG and WebP input images will not take advantage of the shrink-on-load performance optimisation
when applying a gamma correction.
**Parameters**
- `gamma` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** value between 1.0 and 3.0. (optional, default `2.2`)
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# negate
Produce the "negative" of the image.
**Parameters**
- `negate` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**
# normalise
Enhance output image contrast by stretching its luminance to cover the full dynamic range.
**Parameters**
- `normalise` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**
# normalize
Alternative spelling of normalise.
**Parameters**
- `normalize` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**
# convolve
Convolve the image with the specified kernel.
**Parameters**
- `kernel` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)**
- `kernel.width` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** width of the kernel in pixels.
- `kernel.height` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** width of the kernel in pixels.
- `kernel.kernel` **[Array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array)** Array of length `width*height` containing the kernel values.
- `kernel.scale` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the scale of the kernel in pixels. (optional, default `sum`)
- `kernel.offset` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the offset of the kernel in pixels. (optional, default `0`)
**Examples**
```javascript
sharp(input)
.convolve({
width: 3,
height: 3,
kernel: [-1, 0, 1, -2, 0, 2, -1, 0, 1]
})
.raw()
.toBuffer(function(err, data, info) {
// data contains the raw pixel data representing the convolution
// of the input image with the horizontal Sobel operator
});
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# threshold
Any pixel value greather than or equal to the threshold value will be set to 255, otherwise it will be set to 0.
**Parameters**
- `threshold` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** a value in the range 0-255 representing the level at which the threshold will be applied. (optional, default `128`)
- `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]**
- `options.greyscale` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** convert to single channel greyscale. (optional, default `true`)
- `options.grayscale` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** alternative spelling for greyscale. (optional, default `true`)
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# boolean
Perform a bitwise boolean operation with operand image.
This operation creates an output image where each pixel is the result of
the selected bitwise boolean `operation` between the corresponding pixels of the input images.
**Parameters**
- `operand` **([Buffer](https://nodejs.org/api/buffer.html) \| [String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String))** Buffer containing image data or String containing the path to an image file.
- `operator` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** one of `and`, `or` or `eor` to perform that bitwise operation, like the C logic operators `&`, `|` and `^` respectively.
- `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]**
- `options.raw` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** describes operand when using raw pixel data.
- `options.raw.width` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- `options.raw.height` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- `options.raw.channels` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**

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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, TIFF, DZI, and libvips' V format supported.
Note that raw pixel data is only supported for buffer output.
A Promises/A+ promise is returned when `callback` is not provided.
**Parameters**
- `fileOut` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** the path to write the image data to.
- `callback` **\[[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)]** called on completion with two arguments `(err, info)`.
`info` contains the output image `format`, `size` (bytes), `width`, `height` and `channels`.
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **[Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise)** when no callback is provided
# toBuffer
Write output to a Buffer.
By default, the format will match the input image. JPEG, PNG, WebP, and RAW are supported.
`callback`, if present, gets three arguments `(err, buffer, info)` where:
- `err` is an error message, if any.
- `buffer` is the output image data.
- `info` contains the output image `format`, `size` (bytes), `width`, `height` and `channels`.
A Promises/A+ promise is returned when `callback` is not provided.
**Parameters**
- `callback` **\[[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)]**
Returns **[Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise)** when no callback is provided
# withMetadata
Include all metadata (EXIF, XMP, IPTC) from the input image in the output image.
The default behaviour, when `withMetadata` is not used, is to strip all metadata and convert to the device-independent sRGB colour space.
This will also convert to and add a web-friendly sRGB ICC profile.
**Parameters**
- `withMetadata` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]**
- `withMetadata.orientation` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** value between 1 and 8, used to update the EXIF `Orientation` tag.
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# jpeg
Use these JPEG options for output image.
**Parameters**
- `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** output options
- `options.quality` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** quality, integer 1-100 (optional, default `80`)
- `options.progressive` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** use progressive (interlace) scan (optional, default `false`)
- `options.chromaSubsampling` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** set to '4:4:4' to prevent chroma subsampling when quality &lt;= 90 (optional, default `'4:2:0'`)
- `options.force` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** force JPEG output, otherwise attempt to use input format (optional, default `true`)
- `trellisQuantisation` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** apply trellis quantisation, requires mozjpeg (optional, default `false`)
- `overshootDeringing` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** apply overshoot deringing, requires mozjpeg (optional, default `false`)
- `optimiseScans` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** optimise progressive scans, forces progressive, requires mozjpeg (optional, default `false`)
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid options
Returns **Sharp**
# png
Use these PNG options for output image.
**Parameters**
- `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]**
- `options.progressive` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** use progressive (interlace) scan (optional, default `false`)
- `options.compressionLevel` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** zlib compression level (optional, default `6`)
- `options.adaptiveFiltering` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** use adaptive row filtering (optional, default `true`)
- `options.force` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** force PNG output, otherwise attempt to use input format (optional, default `true`)
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid options
Returns **Sharp**
# webp
Use these WebP options for output image.
**Parameters**
- `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** output options
- `options.quality` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** quality, integer 1-100 (optional, default `80`)
- `options.force` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** force WebP output, otherwise attempt to use input format (optional, default `true`)
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid options
Returns **Sharp**
# tiff
Use these TIFF options for output image.
**Parameters**
- `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** output options
- `options.quality` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** quality, integer 1-100 (optional, default `80`)
- `options.force` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** force TIFF output, otherwise attempt to use input format (optional, default `true`)
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid options
Returns **Sharp**
# raw
Force output to be raw, uncompressed uint8 pixel data.
Returns **Sharp**
# toFormat
Force output to a given format.
**Parameters**
- `format` **([String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String) \| [Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object))** as a String or an Object with an 'id' attribute
- `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)** output options
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** unsupported format or options
Returns **Sharp**
# tile
Use tile-based deep zoom (image pyramid) output.
You can also use a `.zip` or `.szi` file extension with `toFile` to write to a compressed archive file format.
**Parameters**
- `tile` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]**
- `tile.size` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** tile size in pixels, a value between 1 and 8192. (optional, default `256`)
- `tile.overlap` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** tile overlap in pixels, a value between 0 and 8192. (optional, default `0`)
- `tile.container` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** tile container, with value `fs` (filesystem) or `zip` (compressed file). (optional, default `'fs'`)
- `tile.layout` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** filesystem layout, possible values are `dz`, `zoomify` or `google`. (optional, default `'dz'`)
**Examples**
```javascript
sharp('input.tiff')
.tile({
size: 512
})
.toFile('output.dzi', function(err, info) {
// output.dzi is the Deep Zoom XML definition
// output_files contains 512x512 tiles grouped by zoom level
});
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**

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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
# resize
Resize image to `width` x `height`.
By default, the resized image is centre cropped to the exact size specified.
Possible reduction kernels are:
- `cubic`: Use a [Catmull-Rom spline](https://en.wikipedia.org/wiki/Centripetal_Catmull%E2%80%93Rom_spline).
- `lanczos2`: Use a [Lanczos kernel](https://en.wikipedia.org/wiki/Lanczos_resampling#Lanczos_kernel) with `a=2`.
- `lanczos3`: Use a Lanczos kernel with `a=3` (the default).
Possible enlargement interpolators are:
- `nearest`: Use [nearest neighbour interpolation](http://en.wikipedia.org/wiki/Nearest-neighbor_interpolation).
- `bilinear`: Use [bilinear interpolation](http://en.wikipedia.org/wiki/Bilinear_interpolation), faster than bicubic but with less smooth results.
- `vertexSplitQuadraticBasisSpline`: Use the smoother [VSQBS interpolation](https://github.com/jcupitt/libvips/blob/master/libvips/resample/vsqbs.cpp#L48) to prevent "staircasing" when enlarging.
- `bicubic`: Use [bicubic interpolation](http://en.wikipedia.org/wiki/Bicubic_interpolation) (the default).
- `locallyBoundedBicubic`: Use [LBB interpolation](https://github.com/jcupitt/libvips/blob/master/libvips/resample/lbb.cpp#L100), which prevents some "[acutance](http://en.wikipedia.org/wiki/Acutance)" but typically reduces performance by a factor of 2.
- `nohalo`: Use [Nohalo interpolation](http://eprints.soton.ac.uk/268086/), which prevents acutance but typically reduces performance by a factor of 3.
**Parameters**
- `width` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** pixels wide the resultant image should be, between 1 and 16383 (0x3FFF). Use `null` or `undefined` to auto-scale the width to match the height.
- `height` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** pixels high the resultant image should be, between 1 and 16383. Use `null` or `undefined` to auto-scale the height to match the width.
- `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]**
- `options.kernel` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** the kernel to use for image reduction. (optional, default `'lanczos3'`)
- `options.interpolator` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** the interpolator to use for image enlargement. (optional, default `'bicubic'`)
**Examples**
```javascript
sharp(inputBuffer)
.resize(200, 300, {
kernel: sharp.kernel.lanczos2,
interpolator: sharp.interpolator.nohalo
})
.background('white')
.embed()
.toFile('output.tiff')
.then(function() {
// output.tiff is a 200 pixels wide and 300 pixels high image
// containing a lanczos2/nohalo scaled version, embedded on a white canvas,
// of the image data in inputBuffer
});
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# crop
Crop the resized image to the exact size specified, the default behaviour.
Possible attributes of the optional `sharp.gravity` are `north`, `northeast`, `east`, `southeast`, `south`,
`southwest`, `west`, `northwest`, `center` and `centre`.
The experimental strategy-based approach resizes so one dimension is at its target length
then repeatedly ranks edge regions, discarding the edge with the lowest score based on the selected strategy.
- `entropy`: focus on the region with the highest [Shannon entropy](https://en.wikipedia.org/wiki/Entropy_%28information_theory%29).
- `attention`: focus on the region with the highest luminance frequency, colour saturation and presence of skin tones.
**Parameters**
- `crop` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** A member of `sharp.gravity` to crop to an edge/corner or `sharp.strategy` to crop dynamically. (optional, default `'centre'`)
**Examples**
```javascript
const transformer = sharp()
.resize(200, 200)
.crop(sharp.strategy.entropy)
.on('error', function(err) {
console.log(err);
});
// Read image data from readableStream
// Write 200px square auto-cropped image data to writableStream
readableStream.pipe(transformer).pipe(writableStream);
```
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
Returns **Sharp**
# embed
Preserving aspect ratio, resize the image to the maximum `width` or `height` specified
then embed on a background of the exact `width` and `height` specified.
If the background contains an alpha value then WebP and PNG format output images will
contain an alpha channel, even when the input image does not.
**Examples**
```javascript
sharp('input.gif')
.resize(200, 300)
.background({r: 0, g: 0, b: 0, a: 0})
.embed()
.toFormat(sharp.format.webp)
.toBuffer(function(err, outputBuffer) {
if (err) {
throw err;
}
// outputBuffer contains WebP image data of a 200 pixels wide and 300 pixels high
// containing a scaled version, embedded on a transparent canvas, of input.gif
});
```
Returns **Sharp**
# max
Preserving aspect ratio, resize the image to be as large as possible
while ensuring its dimensions are less than or equal to the `width` and `height` specified.
Both `width` and `height` must be provided via `resize` otherwise the behaviour will default to `crop`.
**Examples**
```javascript
sharp(inputBuffer)
.resize(200, 200)
.max()
.toFormat('jpeg')
.toBuffer()
.then(function(outputBuffer) {
// outputBuffer contains JPEG image data no wider than 200 pixels and no higher
// than 200 pixels regardless of the inputBuffer image dimensions
});
```
Returns **Sharp**
# min
Preserving aspect ratio, resize the image to be as small as possible
while ensuring its dimensions are greater than or equal to the `width` and `height` specified.
Both `width` and `height` must be provided via `resize` otherwise the behaviour will default to `crop`.
Returns **Sharp**
# ignoreAspectRatio
Ignoring the aspect ratio of the input, stretch the image to
the exact `width` and/or `height` provided via `resize`.
Returns **Sharp**
# withoutEnlargement
Do not enlarge the output image if the input image width _or_ height are already less than the required dimensions.
This is equivalent to GraphicsMagick's `>` geometry option:
"_change the dimensions of the image only if its width or height exceeds the geometry specification_".
**Parameters**
- `withoutEnlargement` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `true`)
Returns **Sharp**

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# cache
Gets, or when options are provided sets, the limits of _libvips'_ operation cache.
Existing entries in the cache will be trimmed after any change in limits.
This method always returns cache statistics,
useful for determining how much working memory is required for a particular task.
**Parameters**
- `Object` **([Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object) \| [Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean))** with the following attributes, or Boolean where true uses default cache settings and false removes all caching.
- `options`
- `options.memory` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** is the maximum memory in MB to use for this cache (optional, default `50`)
- `options.files` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** is the maximum number of files to hold open (optional, default `20`)
- `options.items` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** is the maximum number of operations to cache (optional, default `100`)
**Examples**
```javascript
const stats = sharp.cache();
```
```javascript
sharp.cache( { items: 200 } );
sharp.cache( { files: 0 } );
sharp.cache(false);
```
Returns **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)**
# concurrency
Gets, or when a concurrency is provided sets,
the number of threads _libvips'_ should create to process each image.
The default value is the number of CPU cores.
A value of `0` will reset to this default.
The maximum number of images that can be processed in parallel
is limited by libuv's `UV_THREADPOOL_SIZE` environment variable.
This method always returns the current concurrency.
**Parameters**
- `concurrency` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]**
**Examples**
```javascript
const threads = sharp.concurrency(); // 4
sharp.concurrency(2); // 2
sharp.concurrency(0); // 4
```
Returns **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** concurrency
# counters
Provides access to internal task counters.
- queue is the number of tasks this module has queued waiting for _libuv_ to provide a worker thread from its pool.
- process is the number of resize tasks currently being processed.
**Examples**
```javascript
const counters = sharp.counters(); // { queue: 2, process: 4 }
```
Returns **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)**
# simd
Get and set use of SIMD vector unit instructions.
Requires libvips to have been compiled with liborc support.
Improves the performance of `resize`, `blur` and `sharpen` operations
by taking advantage of the SIMD vector unit of the CPU, e.g. Intel SSE and ARM NEON.
This feature is currently off by default but future versions may reverse this.
Versions of liborc prior to 0.4.25 are known to segfault under heavy load.
**Parameters**
- `simd` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** (optional, default `false`)
**Examples**
```javascript
const simd = sharp.simd();
// simd is `true` if SIMD is currently enabled
```
```javascript
const simd = sharp.simd(true);
// attempts to enable the use of SIMD, returning true if available
```
Returns **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)**

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# API
```javascript
var sharp = require('sharp');
```
### Input
#### sharp([input], [options])
Constructor to which further methods are chained.
`input`, if present, can be one of:
* Buffer containing JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data, or
* String containing the path to an JPEG, PNG, WebP, GIF, SVG or TIFF image file.
JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data
can be streamed into the object when `input` is `null` or `undefined`.
`options`, if present, is an Object with the following optional attributes:
* `density` an integral number representing the DPI for vector images, defaulting to 72.
* `raw` an Object containing `width`, `height` and `channels` when providing uncompressed data. See `raw()` for pixel ordering.
The object returned by the constructor implements the
[stream.Duplex](http://nodejs.org/api/stream.html#stream_class_stream_duplex) class.
JPEG, PNG or WebP format image data can be streamed out from this object.
When using Stream based output, derived attributes are available from the `info` event.
```javascript
sharp('input.jpg')
.resize(300, 200)
.toFile('output.jpg', function(err) {
// output.jpg is a 300 pixels wide and 200 pixels high image
// containing a scaled and cropped version of input.jpg
});
```
```javascript
// Read image data from readableStream,
// resize to 300 pixels wide,
// emit an 'info' event with calculated dimensions
// and finally write image data to writableStream
var transformer = sharp()
.resize(300)
.on('info', function(info) {
console.log('Image height is ' + info.height);
});
readableStream.pipe(transformer).pipe(writableStream);
```
#### metadata([callback])
Fast access to image metadata without decoding any compressed image data.
`callback`, if present, gets the arguments `(err, metadata)` where `metadata` has the attributes:
* `format`: Name of decoder used to decompress image data e.g. `jpeg`, `png`, `webp`, `gif`, `svg`
* `width`: Number of pixels wide
* `height`: Number of pixels high
* `space`: Name of colour space interpretation e.g. `srgb`, `rgb`, `scrgb`, `cmyk`, `lab`, `xyz`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L568)
* `channels`: Number of bands e.g. `3` for sRGB, `4` for CMYK
* `density`: Number of pixels per inch (DPI), if present
* `hasProfile`: Boolean indicating the presence of an embedded ICC profile
* `hasAlpha`: Boolean indicating the presence of an alpha transparency channel
* `orientation`: Number value of the EXIF Orientation header, if present
* `exif`: Buffer containing raw EXIF data, if present
* `icc`: Buffer containing raw [ICC](https://www.npmjs.com/package/icc) profile data, if present
A Promises/A+ promise is returned when `callback` is not provided.
```javascript
var image = sharp(inputJpg);
image
.metadata()
.then(function(metadata) {
return image
.resize(Math.round(metadata.width / 2))
.webp()
.toBuffer();
})
.then(function(data) {
// data contains a WebP image half the width and height of the original JPEG
});
```
#### clone()
Takes a "snapshot" of the instance, returning a new instance.
Cloned instances inherit the input of their parent instance.
This allows multiple output Streams
and therefore multiple processing pipelines
to share a single input Stream.
```javascript
var pipeline = sharp().rotate();
pipeline.clone().resize(800, 600).pipe(firstWritableStream);
pipeline.clone().extract({ left: 20, top: 20, width: 100, height: 100 }).pipe(secondWritableStream);
readableStream.pipe(pipeline);
// firstWritableStream receives auto-rotated, resized readableStream
// secondWritableStream receives auto-rotated, extracted region of readableStream
```
#### sequentialRead()
An advanced setting that switches the libvips access method to `VIPS_ACCESS_SEQUENTIAL`.
This will reduce memory usage and can improve performance on some systems.
#### limitInputPixels(pixels)
Do not process input images where the number of pixels (width * height) exceeds this limit.
`pixels` is either an integral Number of pixels, with a value between 1 and the default 268402689 (0x3FFF * 0x3FFF) or
a boolean. `false` will disable checking while `true` will revert to the default limit.
### Resizing
#### resize([width], [height], [options])
Scale output to `width` x `height`. By default, the resized image is cropped to the exact size specified.
`width` is the integral Number of pixels wide the resultant image should be, between 1 and 16383 (0x3FFF). Use `null` or `undefined` to auto-scale the width to match the height.
`height` is the integral Number of pixels high the resultant image should be, between 1 and 16383. Use `null` or `undefined` to auto-scale the height to match the width.
`options` is an optional Object. If present, it can contain one or more of:
* `options.kernel`, the kernel to use for image reduction, defaulting to `lanczos3`.
* `options.interpolator`, the interpolator to use for image enlargement, defaulting to `bicubic`.
Possible kernels are:
* `cubic`: Use a [Catmull-Rom spline](https://en.wikipedia.org/wiki/Centripetal_Catmull%E2%80%93Rom_spline).
* `lanczos2`: Use a [Lanczos kernel](https://en.wikipedia.org/wiki/Lanczos_resampling#Lanczos_kernel) with `a=2`.
* `lanczos3`: Use a Lanczos kernel with `a=3` (the default).
Possible interpolators are:
* `nearest`: Use [nearest neighbour interpolation](http://en.wikipedia.org/wiki/Nearest-neighbor_interpolation).
* `bilinear`: Use [bilinear interpolation](http://en.wikipedia.org/wiki/Bilinear_interpolation), faster than bicubic but with less smooth results.
* `vertexSplitQuadraticBasisSpline`: Use the smoother [VSQBS interpolation](https://github.com/jcupitt/libvips/blob/master/libvips/resample/vsqbs.cpp#L48) to prevent "staircasing" when enlarging.
* `bicubic`: Use [bicubic interpolation](http://en.wikipedia.org/wiki/Bicubic_interpolation) (the default).
* `locallyBoundedBicubic`: Use [LBB interpolation](https://github.com/jcupitt/libvips/blob/master/libvips/resample/lbb.cpp#L100), which prevents some "[acutance](http://en.wikipedia.org/wiki/Acutance)" but typically reduces performance by a factor of 2.
* `nohalo`: Use [Nohalo interpolation](http://eprints.soton.ac.uk/268086/), which prevents acutance but typically reduces performance by a factor of 3.
```javascript
sharp(inputBuffer)
.resize(200, 300, {
kernel: sharp.kernel.lanczos2,
interpolator: sharp.interpolator.nohalo
})
.background('white')
.embed()
.toFile('output.tiff')
.then(function() {
// output.tiff is a 200 pixels wide and 300 pixels high image
// containing a lanczos2/nohalo scaled version, embedded on a white canvas,
// of the image data in inputBuffer
});
```
#### crop([option])
Crop the resized image to the exact size specified, the default behaviour.
`option`, if present, is an attribute of:
* `sharp.gravity` e.g. `sharp.gravity.north`, to crop to an edge or corner, or
* `sharp.strategy` e.g. `sharp.strategy.entropy`, to crop dynamically.
Possible attributes of `sharp.gravity` are
`north`, `northeast`, `east`, `southeast`, `south`,
`southwest`, `west`, `northwest`, `center` and `centre`.
The experimental strategy-based approach resizes so one dimension is at its target length
then repeatedly ranks edge regions, discarding the edge with the lowest score based on the selected strategy.
* `entropy`: focus on the region with the highest [Shannon entropy](https://en.wikipedia.org/wiki/Entropy_%28information_theory%29).
* `attention`: focus on the region with the highest luminance frequency, colour saturation and presence of skin tones.
The default crop option is a `center`/`centre` gravity.
```javascript
var transformer = sharp()
.resize(200, 200)
.crop(sharp.strategy.entropy)
.on('error', function(err) {
console.log(err);
});
// Read image data from readableStream
// Write 200px square auto-cropped image data to writableStream
readableStream.pipe(transformer).pipe(writableStream);
```
#### embed()
Preserving aspect ratio, resize the image to the
maximum `width` or `height` specified
then embed on a background of the exact
`width` and `height` specified.
If the background contains an alpha value
then WebP and PNG format output images will
contain an alpha channel,
even when the input image does not.
```javascript
sharp('input.gif')
.resize(200, 300)
.background({r: 0, g: 0, b: 0, a: 0})
.embed()
.toFormat(sharp.format.webp)
.toBuffer(function(err, outputBuffer) {
if (err) {
throw err;
}
// outputBuffer contains WebP image data of a 200 pixels wide and 300 pixels high
// containing a scaled version, embedded on a transparent canvas, of input.gif
});
```
#### max()
Preserving aspect ratio,
resize the image to be as large as possible
while ensuring its dimensions are less than or equal to
the `width` and `height` specified.
Both `width` and `height` must be provided via
`resize` otherwise the behaviour will default to `crop`.
```javascript
sharp(inputBuffer)
.resize(200, 200)
.max()
.toFormat('jpeg')
.toBuffer()
.then(function(outputBuffer) {
// outputBuffer contains JPEG image data no wider than 200 pixels and no higher
// than 200 pixels regardless of the inputBuffer image dimensions
});
```
#### min()
Preserving aspect ratio,
resize the image to be as small as possible
while ensuring its dimensions are greater than or equal to
the `width` and `height` specified.
Both `width` and `height` must be provided via `resize` otherwise the behaviour will default to `crop`.
#### withoutEnlargement()
Do not enlarge the output image
if the input image width *or* height
are already less than the required dimensions.
This is equivalent to GraphicsMagick's `>` geometry option:
"*change the dimensions of the image only
if its width or height exceeds the geometry specification*".
#### ignoreAspectRatio()
Ignoring the aspect ratio of the input, stretch the image to the exact `width` and/or `height` provided via `resize`.
### Operations
#### extract({ left: left, top: top, width: width, height: height })
Extract a region of the image. Can be used with or without a `resize` operation.
`left` and `top` are the offset, in pixels, from the top-left corner.
`width` and `height` are the dimensions of the extracted image.
Use `extract` before `resize` for pre-resize extraction. Use `extract` after `resize` for post-resize extraction. Use `extract` before and after for both.
```javascript
sharp(input)
.extract({ left: left, top: top, width: width, height: height })
.toFile(output, function(err) {
// Extract a region of the input image, saving in the same format.
});
```
```javascript
sharp(input)
.extract({ left: leftOffsetPre, top: topOffsetPre, width: widthPre, height: heightPre })
.resize(width, height)
.extract({ left: leftOffsetPost, top: topOffsetPost, width: widthPost, height: heightPost })
.toFile(output, function(err) {
// Extract a region, resize, then extract from the resized image
});
```
#### trim([tolerance])
Trim "boring" pixels from all edges that contain values within a percentage similarity of the top-left pixel.
* `tolerance`, if present, is an integral Number between 1 and 99 representing the percentage similarity, defaulting to 10.
#### background(rgba)
Set the background for the `embed`, `flatten` and `extend` operations.
`rgba` is parsed by the [color](https://www.npmjs.org/package/color) module to extract values for red, green, blue and alpha.
The alpha value is a float between `0` (transparent) and `1` (opaque).
The default background is `{r: 0, g: 0, b: 0, a: 1}`, black without transparency.
#### flatten()
Merge alpha transparency channel, if any, with `background`.
#### extend(extension)
Extends/pads the edges of the image with `background`, where `extension` is one of:
* a Number representing the pixel count to add to each edge, or
* an Object containing `top`, `left`, `bottom` and `right` attributes, each a Number of pixels to add to that edge.
This operation will always occur after resizing and extraction, if any.
```javascript
// Resize to 140 pixels wide, then add 10 transparent pixels
// to the top, left and right edges and 20 to the bottom edge
sharp(input)
.resize(140)
.background({r: 0, g: 0, b: 0, a: 0})
.extend({top: 10, bottom: 20, left: 10, right: 10})
...
```
#### negate()
Produces the "negative" of the image. White => Black, Black => White, Blue => Yellow, etc.
#### rotate([angle])
Rotate the output image by either an explicit angle or auto-orient based on the EXIF `Orientation` tag.
`angle`, if present, is a Number with a value of `0`, `90`, `180` or `270`.
Use this method without `angle` to determine the angle from EXIF data. Mirroring is supported and may infer the use of a `flip` operation.
Method order is important when both rotating and extracting regions, for example `rotate(x).extract(y)` will produce a different result to `extract(y).rotate(x)`.
The use of `rotate` implies the removal of the EXIF `Orientation` tag, if any.
```javascript
var pipeline = sharp()
.rotate()
.resize(null, 200)
.progressive()
.toBuffer(function(err, outputBuffer, info) {
if (err) {
throw err;
}
// outputBuffer contains 200px high progressive JPEG image data,
// auto-rotated using EXIF Orientation tag
// info.width and info.height contain the dimensions of the resized image
});
readableStream.pipe(pipeline);
```
#### flip()
Flip the image about the vertical Y axis. This always occurs after rotation, if any.
The use of `flip` implies the removal of the EXIF `Orientation` tag, if any.
#### flop()
Flop the image about the horizontal X axis. This always occurs after rotation, if any.
The use of `flop` implies the removal of the EXIF `Orientation` tag, if any.
#### blur([sigma])
When used without parameters, performs a fast, mild blur of the output image. This typically reduces performance by 10%.
When a `sigma` is provided, performs a slower, more accurate Gaussian blur. This typically reduces performance by 25%.
* `sigma`, if present, is a Number between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
#### convolve(kernel)
Convolve the image with the specified `kernel`, an Object with the following attributes:
* `width` is an integral Number representing the width of the kernel in pixels.
* `height` is an integral Number representing the width of the kernel in pixels.
* `kernel` is an Array of length `width*height` containing the kernel values.
* `scale`, if present, is a Number representing the scale of the kernel in pixels, defaulting to the sum of the kernel's values.
* `offset`, if present, is a Number representing the offset of the kernel in pixels, defaulting to 0.
```javascript
sharp(input)
.convolve({
width: 3,
height: 3,
kernel: [-1, 0, 1, -2, 0, 2, -1, 0, 1]
})
.raw()
.toBuffer(function(err, data, info) {
// data contains the raw pixel data representing the convolution
// of the input image with the horizontal Sobel operator
});
```
#### sharpen([sigma], [flat], [jagged])
When used without parameters, performs a fast, mild sharpen of the output image. This typically reduces performance by 10%.
When a `sigma` is provided, performs a slower, more accurate sharpen of the L channel in the LAB colour space. Separate control over the level of sharpening in "flat" and "jagged" areas is available. This typically reduces performance by 50%.
* `sigma`, if present, is a Number representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
* `flat`, if present, is a Number representing the level of sharpening to apply to "flat" areas, defaulting to a value of 1.0.
* `jagged`, if present, is a Number representing the level of sharpening to apply to "jagged" areas, defaulting to a value of 2.0.
#### threshold([threshold], [options])
Any pixel value greather than or equal to the threshold value will be set to 255, otherwise it will be set to 0.
By default, the image will be converted to single channel greyscale before thresholding.
* `threshold`, if present, is a Number between 0 and 255, representing the level at which the threshold will be applied. The default threshold is 128.
* `options`, if present, is an Object containing a Boolean `greyscale` (or `grayscale`). When `false` each channel will have the threshold applied independently.
#### gamma([gamma])
Apply a gamma correction by reducing the encoding (darken) pre-resize at a factor of `1/gamma` then increasing the encoding (brighten) post-resize at a factor of `gamma`.
`gamma`, if present, is a Number between 1 and 3. The default value is `2.2`, a suitable approximation for sRGB images.
This can improve the perceived brightness of a resized image in non-linear colour spaces.
JPEG input images will not take advantage of the shrink-on-load performance optimisation when applying a gamma correction.
#### grayscale() / greyscale()
Convert to 8-bit greyscale; 256 shades of grey.
This is a linear operation. If the input image is in a non-linear colour space such as sRGB, use `gamma()` with `greyscale()` for the best results.
By default the output image will be web-friendly sRGB and contain three (identical) color channels. This may be overridden by other sharp operations such as `toColourspace('b-w')`, which will produce an output image containing one color channel. An alpha channel may be present, and will be unchanged by the operation.
#### normalize() / normalise()
Enhance output image contrast by stretching its luminance to cover the full dynamic range. This typically reduces performance by 30%.
#### overlayWith(image, [options])
Overlay (composite) a image over the processed (resized, extracted etc.) image.
`image` is one of the following, and must be the same size or smaller than the processed image:
* Buffer containing image data, or
* String containing the path to an image file
`options`, if present, is an Object with the following optional attributes:
* `gravity` is a String or an attribute of the `sharp.gravity` Object e.g. `sharp.gravity.north` at which to place the overlay, defaulting to `center`/`centre`.
* `top` is an integral Number representing the pixel offset from the top edge.
* `left` is an integral Number representing the pixel offset from the left edge.
* `tile` is a Boolean, defaulting to `false`. When set to `true` repeats the overlay image across the entire image with the given `gravity`.
* `cutout` is a Boolean, defaulting to `false`. When set to `true` applies only the alpha channel of the overlay image to the image to be overlaid, giving the appearance of one image being cut out of another.
* `raw` an Object containing `width`, `height` and `channels` when providing uncompressed data.
If both `top` and `left` are provided, they take precedence over `gravity`.
```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!
});
```
#### toColourspace(colourspace) / toColorspace(colorspace)
Set the output colourspace. By default output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.
`colourspace` is a string or `sharp.colourspace` enum that identifies an output colourspace. String arguments comprise vips colour space interpretation names e.g. `srgb`, `rgb`, `scrgb`, `cmyk`, `lab`, `xyz`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L568)
#### extractChannel(channel)
Extract a single channel from a multi-channel image.
`channel` is a zero-indexed integral Number representing the band number to extract. `red`, `green` or `blue` are also accepted as an alternative to `0`, `1` or `2` respectively.
```javascript
sharp(input)
.extractChannel('green')
.toFile('input_green.jpg', function(err, info) {
// info.channels === 1
// input_green.jpg contains the green channel of the input image
});
```
#### joinChannel(channels, [options])
Join a data channel to the image. The meaning of the added channels depends on the output colourspace, set with `toColourspace()`. By default the output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.
`channels` is one of
* a single file path
* an array of file paths
* a single buffer
* an array of buffers
Note that channel ordering follows vips convention:
* sRGB: 0: Red, 1: Green, 2: Blue, 3: Alpha
* CMYK: 0: Magenta, 1: Cyan, 2: Yellow, 3: Black, 4: Alpha
Buffers may be any of the image formats supported by sharp: JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data. In the case of a RAW buffer, the `options` object should contain a `raw` attribute, which follows the format of the attribute of the same name in the `sharp()` constructor. See `sharp()` for details. See `raw()` for pixel ordering.
#### bandbool(operation)
Perform a bitwise boolean operation on all input image channels (bands) to produce a single channel output image.
`operation` is a string containing the name of the bitwise operator to be appled to image channels, which can be one of:
* `and` performs a bitwise and operation, like the c-operator `&`.
* `or` performs a bitwise or operation, like the c-operator `|`.
* `eor` performs a bitwise exclusive or operation, like the c-operator `^`.
```javascript
sharp('input.png')
.bandbool(sharp.bool.and)
.toFile('output.png')
```
In the above example if `input.png` is a 3 channel RGB image, `output.png` will be a 1 channel grayscale image where each pixel `P = R & G & B`.
For example, if `I(1,1) = [247, 170, 14] = [0b11110111, 0b10101010, 0b00001111]` then `O(1,1) = 0b11110111 & 0b10101010 & 0b00001111 = 0b00000010 = 2`.
#### boolean(image, operation, [options])
Perform a bitwise boolean operation with `image`, where `image` is one of the following:
* Buffer containing JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data, or
* String containing the path to an image file
This operation creates an output image where each pixel is the result of the selected bitwise boolean `operation` between the corresponding pixels of the input images.
The boolean operation can be one of the following:
* `and` performs a bitwise and operation, like the c-operator `&`.
* `or` performs a bitwise or operation, like the c-operator `|`.
* `eor` performs a bitwise exclusive or operation, like the c-operator `^`.
`options`, if present, is an Object with the following optional attributes:
* `raw` an Object containing `width`, `height` and `channels` when providing uncompressed data.
### Output
#### toFile(path, [callback])
`path` is a String containing the path to write the image data to.
If an explicit output format is not selected, it will be inferred from the extension, with JPEG, PNG, WebP, TIFF, DZI, and VIPS V format supported. Note that RAW format is only supported for buffer output.
`callback`, if present, is called with two arguments `(err, info)` where:
* `err` contains an error message, if any.
* `info` contains the output image `format`, `size` (bytes), `width`, `height` and `channels`.
A Promises/A+ promise is returned when `callback` is not provided.
#### toBuffer([callback])
Write image data to a Buffer, the format of which will match the input image by default. JPEG, PNG, WebP, and RAW are supported.
`callback`, if present, gets three arguments `(err, buffer, info)` where:
* `err` is an error message, if any.
* `buffer` is the output image data.
* `info` contains the output image `format`, `size` (bytes), `width`, `height` and `channels`.
A Promises/A+ promise is returned when `callback` is not provided.
#### jpeg([options])
Use JPEG format for the output image.
`options`, if present, is an Object with the following optional attributes:
* `quality` is an integral Number between 1 and 100, default 80. Using quality >90 forces a `chromaSubsampling` value of '4:4:4'.
* `progressive` is a Boolean to control the use of progressive (interlace) scan, default false.
* `chromaSubsampling` is a String with the value '4:2:0' (default) or '4:4:4' to control [chroma subsampling](http://en.wikipedia.org/wiki/Chroma_subsampling).
* `force` is a Boolean, where true (default) will force the use of JPEG output and false will use the input format.
The following, additional options require libvips to have been compiled with mozjpeg support:
* `trellisQuantisation` / `trellisQuantization` is a Boolean, default false, to control the use of [trellis quantisation](http://en.wikipedia.org/wiki/Trellis_quantization).
* `overshootDeringing` is a Boolean, default false, to reduce the effects of [ringing](http://en.wikipedia.org/wiki/Ringing_%28signal%29).
* `optimiseScans` / `optimizeScans` is a Boolean, default false, when true calculates which spectrum of DCT coefficients uses the fewest bits for each progressive scan.
#### png([options])
Use PNG format for the output image.
`options`, if present, is an Object with the following optional attributes:
* `progressive` is a Boolean to control the use of progressive (interlace) scan, default false.
* `compressionLevel` is an integral Number between 0 and 9, default 6, to set the _zlib_ compression level.
* `adaptiveFiltering` is a Boolean to control [adaptive row filtering](https://en.wikipedia.org/wiki/Portable_Network_Graphics#Filtering), true for adaptive (default), false for none.
* `force` is a Boolean, where true (default) will force the use of PNG output and false will use the input format.
#### webp([options])
Use WebP format for the output image.
`options`, if present, is an Object with the following optional attributes:
* `quality` is an integral Number between 1 and 100, default 80.
* `force` is a Boolean, where true (default) will force the use of WebP output and false will use the input format.
#### tiff([options])
Use TIFF format for the output image.
`options`, if present, is an Object with the following optional attributes:
* `quality` is an integral Number between 1 and 100, default 80.
* `force` is a Boolean, where true (default) will force the use of TIFF output and false will use the input format.
#### raw()
Provide raw, uncompressed uint8 (unsigned char) image data for Buffer and Stream based output.
The number of channels depends on the input image and selected options.
* 1 channel for images converted to `greyscale()`, with each byte representing one pixel.
* 3 channels for colour images without alpha transparency, with bytes ordered \[red, green, blue, red, green, blue, etc.\]).
* 4 channels for colour images with alpha transparency, with bytes ordered \[red, green, blue, alpha, red, green, blue, alpha, etc.\].
#### toFormat(format, [options])
Convenience method for the above output format methods, where `format` is either:
* an attribute of the `sharp.format` Object e.g. `sharp.format.jpeg`, or
* a String containing `jpeg`, `png`, `webp`, `tiff` or `raw`.
#### withMetadata([metadata])
Include all metadata (EXIF, XMP, IPTC) from the input image in the output image.
This will also convert to and add the latest web-friendly v2 sRGB ICC profile.
The optional `metadata` parameter, if present, is an Object with the attributes to update.
New attributes cannot be inserted, only existing attributes updated.
* `orientation` is an integral Number between 1 and 8, used to update the value of the EXIF `Orientation` tag.
This has no effect if the input image does not have an EXIF `Orientation` tag.
The default behaviour, when `withMetadata` is not used, is to strip all metadata and convert to the device-independent sRGB colour space.
#### tile(options)
The size, overlap, container and directory layout to use when generating square Deep Zoom image pyramid tiles.
`options` is an Object with one or more of the following attributes:
* `size` is an integral Number between 1 and 8192. The default value is 256 pixels.
* `overlap` is an integral Number between 0 and 8192. The default value is 0 pixels.
* `container` is a String, with value `fs` or `zip`. The default value is `fs`.
* `layout` is a String, with value `dz`, `zoomify` or `google`. The default value is `dz`.
You can also use the file extension `.zip` or `.szi` to write to a compressed archive file format.
```javascript
sharp('input.tiff')
.tile({
size: 512
})
.toFile('output.dzi', function(err, info) {
// output.dzi is the Deep Zoom XML definition
// output_files contains 512x512 tiles grouped by zoom level
});
```
### Attributes
#### format
An Object containing nested boolean values
representing the available input and output formats/methods,
for example:
```javascript
> console.dir(sharp.format);
{ jpeg: { id: 'jpeg',
input: { file: true, buffer: true, stream: true },
output: { file: true, buffer: true, stream: true } },
png: { id: 'png',
input: { file: true, buffer: true, stream: true },
output: { file: true, buffer: true, stream: true } },
webp: { id: 'webp',
input: { file: true, buffer: true, stream: true },
output: { file: true, buffer: true, stream: true } },
tiff: { id: 'tiff',
input: { file: true, buffer: true, stream: true },
output: { file: true, buffer: false, stream: false } },
raw: { id: 'raw',
input: { file: false, buffer: false, stream: false },
output: { file: false, buffer: true, stream: true } } }
```
#### queue
An EventEmitter that emits a `change` event when a task is either:
* queued, waiting for _libuv_ to provide a worker thread
* complete
```javascript
sharp.queue.on('change', function(queueLength) {
console.log('Queue contains ' + queueLength + ' task(s)');
});
```
#### versions
An Object containing the version numbers of libvips and, on Linux, its dependencies.
```javascript
console.log(sharp.versions);
```
### Utilities
#### sharp.cache([options])
If `options` is provided, sets the limits of _libvips'_ operation cache.
* `options.memory` is the maximum memory in MB to use for this cache, with a default value of 50
* `options.files` is the maximum number of files to hold open, with a default value of 20
* `options.items` is the maximum number of operations to cache, with a default value of 100
`options` can also be a boolean, where `true` enables the default cache settings and `false` disables all caching.
Existing entries in the cache will be trimmed after any change in limits.
This method always returns cache statistics, useful for determining how much working memory is required for a particular task.
```javascript
var stats = sharp.cache();
```
```javascript
sharp.cache( { items: 200 } );
sharp.cache( { files: 0 } );
sharp.cache(false);
```
#### sharp.concurrency([threads])
`threads`, if provided, is the Number of threads _libvips'_ should create for processing each image. The default value is the number of CPU cores. A value of `0` will reset to this default.
This method always returns the current concurrency.
```javascript
var threads = sharp.concurrency(); // 4
sharp.concurrency(2); // 2
sharp.concurrency(0); // 4
```
The maximum number of images that can be processed in parallel is limited by libuv's `UV_THREADPOOL_SIZE` environment variable.
#### sharp.counters()
Provides access to internal task counters.
* `queue` is the number of tasks this module has queued waiting for _libuv_ to provide a worker thread from its pool.
* `process` is the number of resize tasks currently being processed.
```javascript
var counters = sharp.counters(); // { queue: 2, process: 4 }
```
#### sharp.simd([enable])
_Requires libvips to have been compiled with liborc support_
Improves the performance of `resize`, `blur` and `sharpen` operations
by taking advantage of the SIMD vector unit of the CPU, e.g. Intel SSE and ARM NEON.
* `enable`, if present, is a boolean where `true` enables and `false` disables the use of SIMD.
This method always returns the current state.
This feature is currently disabled by default
but future versions may enable it by default.
When enabled, versions of liborc prior to 0.4.24
and versions of libvips prior to 8.2.0
have been known to crash under heavy load.
```javascript
var simd = sharp.simd();
// simd is `true` if SIMD is currently enabled
```
```javascript
var simd = sharp.simd(true);
// attempts to enable the use of SIMD, returning true if available
```

5
docs/install.md
View File

@@ -4,8 +4,13 @@
npm install sharp
```
```sh
yarn add sharp
```
### Prerequisites
* Node v4+
* C++11 compatible compiler such as gcc 4.8+, clang 3.0+ or MSVC 2013+
* [node-gyp](https://github.com/TooTallNate/node-gyp#installation) and its dependencies