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89 lines
3.4 KiB
Markdown
89 lines
3.4 KiB
Markdown
# sharp
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<img src="https://cdn.jsdelivr.net/gh/lovell/sharp@main/docs/image/sharp-logo.svg" width="160" height="160" alt="sharp logo" align="right">
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The typical use case for this high speed Node.js module
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is to convert large images in common formats to
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smaller, web-friendly JPEG, PNG, WebP, GIF and AVIF images of varying dimensions.
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Resizing an image is typically 4x-5x faster than using the
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quickest ImageMagick and GraphicsMagick settings
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due to its use of [libvips](https://github.com/libvips/libvips).
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Colour spaces, embedded ICC profiles and alpha transparency channels are all handled correctly.
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Lanczos resampling ensures quality is not sacrificed for speed.
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As well as image resizing, operations such as
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rotation, extraction, compositing and gamma correction are available.
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Most modern macOS, Windows and Linux systems running Node.js >= 14.15.0
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do not require any additional install or runtime dependencies.
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### Formats
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This module supports reading JPEG, PNG, WebP, GIF, AVIF, TIFF and SVG images.
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Output images can be in JPEG, PNG, WebP, GIF, AVIF and TIFF formats as well as uncompressed raw pixel data.
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Streams, Buffer objects and the filesystem can be used for input and output.
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A single input Stream can be split into multiple processing pipelines and output Streams.
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Deep Zoom image pyramids can be generated,
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suitable for use with "slippy map" tile viewers like
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[OpenSeadragon](https://github.com/openseadragon/openseadragon).
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### Fast
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This module is powered by the blazingly fast
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[libvips](https://github.com/libvips/libvips) image processing library,
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originally created in 1989 at Birkbeck College
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and currently maintained by a small team led by
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[John Cupitt](https://github.com/jcupitt).
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Only small regions of uncompressed image data
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are held in memory and processed at a time,
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taking full advantage of multiple CPU cores and L1/L2/L3 cache.
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Everything remains non-blocking thanks to _libuv_,
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no child processes are spawned and Promises/async/await are supported.
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### Optimal
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The features of `mozjpeg` and `pngquant` can be used
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to optimise the file size of JPEG and PNG images respectively,
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without having to invoke separate `imagemin` processes.
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Huffman tables are optimised when generating JPEG output images
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without having to use separate command line tools like
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[jpegoptim](https://github.com/tjko/jpegoptim) and
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[jpegtran](http://jpegclub.org/jpegtran/).
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PNG filtering is disabled by default,
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which for diagrams and line art often produces the same result
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as [pngcrush](https://pmt.sourceforge.io/pngcrush/).
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The file size of animated GIF output is optimised
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without having to use separate command line tools such as
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[gifsicle](https://www.lcdf.org/gifsicle/).
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### Contributing
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A [guide for contributors](https://github.com/lovell/sharp/blob/main/.github/CONTRIBUTING.md)
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covers reporting bugs, requesting features and submitting code changes.
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### Licensing
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Copyright 2013 Lovell Fuller and others.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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[https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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