sharp

adj

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

The typical use case for this high performance Node.js module is to convert a large JPEG image to smaller JPEG images of varying dimensions.

It is somewhat opinionated in that it only deals with JPEG images, always obeys the requested dimensions by either cropping or embedding and insists on a mild sharpen of the resulting image.

Under the hood you'll find the blazingly fast libvips image processing library, originally created in 1989 at Birkbeck College and currently maintained by the University of Southampton.

Speed is typically 4x faster than the imagemagick equivalent.

Prerequisites

Requires node-gyp and libvips-dev to build.

sudo npm install -g node-gyp
sudo apt-get install libvips-dev

Requires vips-7.xx.pc (installed with libvips-dev) to be symlinked as /usr/lib/pkgconfig/vips.pc

Ubuntu 12.04 LTS:

sudo ln -s /usr/lib/pkgconfig/vips-7.26.pc /usr/lib/pkgconfig/vips.pc

Ubuntu 13.04 (64-bit):

sudo ln -s /usr/lib/x86_64-linux-gnu/pkgconfig/vips-7.28.pc /usr/lib/pkgconfig/vips.pc

Install

npm install sharp

Usage

var sharp = require("sharp");

crop(inputPath, outputPath, width, height, callback)

Scale and crop JPEG inputPath to width x height and write JPEG to outputPath calling callback when complete.

Example:

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

embedWhite(inputPath, outputPath, width, height, callback)

Scale and embed JPEG inputPath to width x height using a white canvas and write JPEG to outputPath calling callback when complete.

sharp.embedWhite("input.jpg", "output.jpg", 200, 300, function(err) {
  if (err) {
    throw err;
  }
  // output.jpg is a 200 pixels wide and 300 pixels high image
  // containing a scaled version of input.jpg embedded on a white canvas
});

embedBlack(inputPath, outputPath, width, height, callback)

Scale and embed JPEG inputPath to width x height using a black canvas and write JPEG to outputPath calling callback when complete.

sharp.embedBlack("input.jpg", "output.jpg", 200, 300, function(err) {
  if (err) {
    throw err;
  }
  // output.jpg is a 200 pixels wide and 300 pixels high image
  // containing a scaled version of input.jpg embedded on a black canvas
});

Testing

npm test

Performance

Using an AMD Athlon quad core CPU with 512KB L2 cache clocked at 3.3GHz with 8GB RAM:

imagemagick x 5.55 ops/sec <20>0.68% (31 runs sampled)
sharp x 24.49 ops/sec <20>6.85% (64 runs sampled)

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