sharp

adj

1. clearly defined; distinct: a sharp photographic image.
2. quick, brisk, or spirited.
3. shrewd or astute: a sharp bargainer.
4. (Informal.) very stylish: a sharp dresser; a sharp jacket.

The typical use case for this high speed Node.js module is to convert large JPEG, PNG, WebP and TIFF images to smaller images of varying dimensions.

The performance of JPEG resizing is typically 15x-25x faster than ImageMagick and GraphicsMagick, based mainly on the number of CPU cores available.

This module supports reading and writing images to and from both the filesystem and Buffer objects (TIFF is limited to filesystem only). Everything remains non-blocking thanks to libuv.

Anyone who has used the Node.js bindings for GraphicsMagick will find the API similarly expressive.

This module is powered by the blazingly fast libvips image processing library, originally created in 1989 at Birkbeck College and currently maintained by John Cupitt.

Prerequisites

• Node.js v0.8+
• libvips v7.38.5+

Install libvips on Mac OS

brew install homebrew/science/vips

Install libvips on Ubuntu/Debian Linux

sudo apt-get install automake build-essential git gobject-introspection gtk-doc-tools libfftw3-dev libglib2.0-dev libjpeg-turbo8-dev libpng12-dev libwebp-dev libtiff5-dev liborc-0.4-dev libxml2-dev swig
git clone https://github.com/jcupitt/libvips.git
cd libvips
./bootstrap.sh
./configure --enable-debug=no
make
sudo make install
sudo ldconfig

Install

npm install sharp

Usage examples

var sharp = require('sharp');

sharp('input.jpg').resize(300, 200).write('output.jpg', function(err) {
  if (err) {
    throw err;
  }
  // output.jpg is a 300 pixels wide and 200 pixels high image
  // containing a scaled and cropped version of input.jpg
});

sharp('input.jpg').resize(null, 200).progressive().toBuffer(function(err, buffer) {
  if (err) {
    throw err;
  }
  // buffer contains progressive JPEG image data, 200 pixels high
});

sharp('input.png').resize(300).sharpen().webp(function(err, buffer) {
  if (err) {
    throw err;
  }
  // buffer contains sharpened WebP image data (converted from PNG), 300 pixels wide
});

sharp(buffer).resize(200, 300).embedWhite().write('output.tiff', function(err) {
  if (err) {
    throw err;
  }
  // output.tiff is a 200 pixels wide and 300 pixels high image containing a scaled
  // version, embedded on a white canvas, of the image data in buffer
});

sharp('input.jpg').resize(200, 300).embedBlack().webp(function(err, buffer) {
  if (err) {
    throw err;
  }
  // buffer contains WebP image data of a 200 pixels wide and 300 pixels high image
  // containing a scaled version, embedded on a black canvas, of input.png
});

API

sharp(input)

Constructor to which further methods are chained.

input can either be a filename String or a Buffer.

resize(width, [height])

Scale to width x height. By default, the resized image is cropped to the exact size specified.

width is the Number of pixels wide the resultant image should be. Use null or undefined to auto-scale the width to match the height.

height is the Number of pixels high the resultant image should be. Use null or undefined to auto-scale the height to match the width.

crop()

Crop the resized image to the exact size specified, the default behaviour.

embedWhite()

Embed the resized image on a white background of the exact size specified.

embedBlack()

Embed the resized image on a black background of the exact size specified.

sharpen()

Perform a mild sharpen of the resultant image. This typically reduces performance by 30%.

progressive()

Use progressive (interlace) scan for the output. This typically reduces performance by 30%.

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.

write(filename, callback)

filename is a String containing the filename to write the image data to. The format is inferred from the extension, with JPEG, PNG, WebP and TIFF supported.

callback is called with a single argument (err) containing an error message, if any.

jpeg(callback)

Write JPEG image data to a Buffer.

callback gets two arguments (err, buffer) where err is an error message, if any, and buffer is the resultant JPEG image data.

png(callback)

Write PNG image data to a Buffer.

callback gets two arguments (err, buffer) where err is an error message, if any, and buffer is the resultant PNG image data.

webp(callback)

Write WebP image data to a Buffer.

callback gets two arguments (err, buffer) where err is an error message, if any, and buffer is the resultant WebP image data.

toBuffer(callback)

Write image data to a Buffer, the format of which will match the input image.

callback gets two arguments (err, buffer) where err is an error message, if any, and buffer is the resultant image data.

sharp.cache([limit])

If limit is provided, set the (soft) limit of libvips working/cache memory to this value in MB. The default value is 100.

This method always returns cache statistics, useful for determining how much working memory is required for a particular task.

Warnings such as Application transferred too many scanlines are a good indicator you've set this value too low.

var stats = sharp.cache(); // { current: 98, high: 115, limit: 100 }
sharp.cache(200); // { current: 98, high: 115, limit: 200 }
sharp.cache(50); // { current: 49, high: 115, limit: 50 }

Testing

npm test

Performance

Test environment:

• AMD Athlon 4 core 3.3GHz 512KB L2 CPU 1333 DDR3
• libvips 7.38
• libjpeg-turbo8 1.3.0
• libpng 1.6.6
• zlib1g 1.2.7
• libwebp 0.3.0
• libtiff 4.0.2

-file-buffer indicates read from file and write to buffer, -buffer-file indicates read from buffer and write to file etc.

-sharpen, -progressive etc. demonstrate the negative effect of options on performance.

JPEG

• imagemagick x 5.53 ops/sec ±0.62% (31 runs sampled)

• gm-file-file x 4.10 ops/sec ±0.41% (25 runs sampled)

• gm-file-buffer x 4.10 ops/sec ±0.36% (25 runs sampled)

• epeg-file-file x 23.82 ops/sec ±0.18% (60 runs sampled)

• epeg-file-buffer x 23.98 ops/sec ±0.16% (61 runs sampled)

• sharp-buffer-file x 20.76 ops/sec ±0.55% (54 runs sampled)

• sharp-buffer-buffer x 20.90 ops/sec ±0.26% (54 runs sampled)

• sharp-file-file x 91.78 ops/sec ±0.38% (88 runs sampled)

• sharp-file-buffer x 93.05 ops/sec ±0.61% (76 runs sampled)

• sharp-file-buffer-sharpen x 63.09 ops/sec ±5.58% (63 runs sampled)

• sharp-file-buffer-progressive x 61.68 ops/sec ±0.53% (76 runs sampled)

• sharp-file-buffer-sequentialRead x 60.66 ops/sec ±0.38% (75 runs sampled)

PNG

• imagemagick x 4.27 ops/sec ±0.21% (25 runs sampled)

• gm-file-file x 8.33 ops/sec ±0.19% (44 runs sampled)

• gm-file-buffer x 7.45 ops/sec ±0.16% (40 runs sampled)

• sharp-buffer-file x 4.94 ops/sec ±118.46% (26 runs sampled)

• sharp-buffer-buffer x 12.59 ops/sec ±0.55% (64 runs sampled)

• sharp-file-file x 44.06 ops/sec ±6.86% (75 runs sampled)

• sharp-file-buffer x 46.29 ops/sec ±0.38% (76 runs sampled)

• sharp-file-buffer-sharpen x 38.86 ops/sec ±0.22% (65 runs sampled)

• sharp-file-buffer-progressive x 46.35 ops/sec ±0.20% (76 runs sampled)

• sharp-file-buffer-sequentialRead x 29.02 ops/sec ±0.62% (72 runs sampled)

WebP

• sharp-buffer-file x 3.30 ops/sec ±117.14% (19 runs sampled)
• sharp-buffer-buffer x 7.66 ops/sec ±5.83% (43 runs sampled)
• sharp-file-file x 9.88 ops/sec ±0.98% (52 runs sampled)
• sharp-file-buffer x 9.95 ops/sec ±0.25% (52 runs sampled)
• sharp-file-buffer-sharpen x 9.05 ops/sec ±0.36% (48 runs sampled)
• sharp-file-buffer-sequentialRead x 9.87 ops/sec ±0.98% (52 runs sampled)

TIFF

• sharp-file-file x 68.24 ops/sec ±5.93% (85 runs sampled)
• sharp-file-file-sharpen x 50.76 ops/sec ±0.52% (82 runs sampled)
• sharp-file-file-sequentialRead x 36.37 ops/sec ±0.90% (87 runs sampled)

Licence

Copyright 2013, 2014 Lovell Fuller

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.