@lord_ne/jpeg-turbo

This is a fork of a fork of jpeg-turbo with the intention of exposing more features of the underlying C library.

node-jpeg-turbo provides minimal libjpeg-turbo bindings for Node.js. It is very, very fast compared to other alternatives, such as node-imagemagick-native or jpeg-js.

Please ask if you need more methods exposed.

Requirements

All versions of Node still in active Long-term Support and the current development version are supported. Older versions may or may not work; they are not and will not be supported.

We provide prebuilds for some platforms, meaning that you should not have to compile native bindings from source very often. The bindings are hosted at and automatically installed from our GitHub Releases. TODO: Figure out how to actually do that.

If you must build from source

First, if you're building from the repo, make sure to init and update submodules or you'll get confusing errors about missing targets when building. We include libjpeg-turbo as a submodule.

git submodule init
git submodule update

(or just use git clone --recursive when cloning the repo)

We build libjpeg-turbo directly with cmake, so both cmake and yasm are required on your machine. yasm is only required on x86 and x86_64 architectures.

To install:

On OS X

brew install yasm
brew install cmake

On Ubuntu/Debian

apt-get install yasm cmake

On Windows

Download and install the latest from here. Make sure to select the option to put it on path for all users.

Download Win32 or Win64 yasm from here and make sure it's found in path as yasm.exe. Use the "for general use" version. If the .exe doesn't run, or complains about a missing MSVCR100.dll, you can install the missing VS2010 Redist x64 from KB2977003. The .exe should work fine after installing the redistributable.

To verify your yasm setup, run:

yasm

This should give the output:

yasm: No input files specified

Next, you need to make sure that you have a build environment set up. An easy way to do that is to use windows-build-tools.

Now, just to make sure things are set up properly, run:

npm config get msvs_version

If the output is 2015 or newer, you're good. If it's anything else, or not set, you must run:

npm config set -g msvs_version 2015

Alternatively, you can specify the option at install time with --msvs_version=2015.

Others

Search your package manager for yasm.

Installation

Make sure you've got the requirements installed first.

Using yarn:

yarn add @lord_ne/jpeg-turbo

Using npm:

npm install --save @lord_ne/jpeg-turbo

API

jpg.bufferSize(options) → Number

If you'd like to preallocate a Buffer for jpg.compressSync(), use this method to get the worst-case upper bound. The options argument is fully compatible with the jpg.compressSync() method, so that you can pass the same options to both functions.

• options is an Object with the following properties:
  • width Required. The width of the image.
  • height Required. The height of the image.
  • subsampling Optional. The subsampling method to use. Defaults to jpg.SAMP_420.
• Returns The Number of bytes required in a worst-case scenario.

var fs = require('fs')
var jpg = require('@lord_ne/jpeg-turbo')

var raw = fs.readFileSync('raw.rgba')

var options = {
  format: jpg.FORMAT_RGBA,
  width: 1080,
  height: 1920,
  subsampling: jpg.SAMP_444,
}

var preallocated = new Buffer(jpg.bufferSize(options))

var encoded = jpg.compressSync(raw, preallocated, options)

jpg.compressSync(raw[, out], options) → Object

Compresses (i.e. encodes) the raw pixel data into a JPG. This method is not capable of resizing the image.

For efficiency reasons you may choose to encode into a preallocated Buffer. While fast, it has a number of drawbacks. Namely, you'll have to be careful not to reuse the buffer in async processing before processing (e.g. saving, displaying or transmitting) the entire encoded image. Otherwise you risk corrupting the image. Also, it wastes a huge amount of space compared to on-demand allocation.

• raw is a Buffer with the raw pixel data in options.format.
• out is an optional preallocated Buffer for the encoded image. The size of the buffer is checked. See jpg.bufferSize() for an example of how to preallocate a sufficient Buffer. If not given, memory is allocated and reallocated as needed, which eliminates most of the wasted space but is slower and lacks consistency with varying source images.
• options is an Object with the following properties:
  • format Required. The format of the raw pixel data (e.g. jpg.FORMAT_RGBA).
  • width Required. The width of the image.
  • height Required. The height of the image.
  • subsampling Optional. The subsampling method to use. Defaults to jpg.SAMP_420.
  • quality Optional. The desired JPG quality. Defaults to 80.
• Returns An Object with the following properties:
  • data The encoded image as a Buffer. Note that the buffer may actually be a slice of the preallocated Buffer, if given. Be careful not to reuse the preallocated buffer before you've finished processing the encoded image, as it may corrupt the image.
  • size The size of the used space in the buffer

var fs = require('fs')
var jpg = require('@lord_ne/jpeg-turbo')

var raw = fs.readFileSync('raw.rgba')

var options = {
  format: jpg.FORMAT_RGBA,
  width: 1080,
  height: 1920,
  subsampling: jpg.SAMP_444,
}

var encoded = jpg.compressSync(raw, options)

See jpg.bufferSize() for an example of preallocated Buffer usage.

jpg.decompressSync(image[, out], options) → Object

Decompresses (i.e. decodes) the JPG image into raw pixel data.

• image is a Buffer with the JPG image data.
• out is an optional preallocated Buffer for the decoded image. The size of the buffer is checked, and should be at least width * height * bytes_per_pixel or larger. If not given, one is created for you. The only benefit of providing the Buffer yourself is that you can reuse the same buffer between multiple jpg.decompressSync() calls. Note that this can lead to issues with concurrency. See jpg.compressSync() for related discussion.
• options is an Object with the following properties:
  • format Required. The desired format of the raw pixel data (e.g. jpg.FORMAT_RGBA).
  • out Deprecated. Use the out argument instead.
• Returns An Object with the following properties:
  • data A Buffer with the raw pixel data.
  • width The width of the image.
  • height The height of the image.
  • subsampling The subsampling method used in the JPG.
  • size Deprecated. Use data.length instead.
  • bpp The number of bytes per pixel.

var fs = require('fs')
var jpg = require('@lord_ne/jpeg-turbo')

var image = fs.readFileSync('image.jpg')

var options = {
  format: jpg.FORMAT_RGBA,
}

var decoded = jpg.decompressSync(image, options)

TODO: API for DCT functions

Thanks

• https://github.com/A2K/node-jpeg-turbo-scaler
• https://github.com/mash/node-imagemagick-native
• https://github.com/google/skia/blob/master/gyp/libjpeg-turbo.gyp
• https://github.com/openstf/android-libjpeg-turbo

License

See LICENSE.

Copyright © Julian Waller. All Rights Reserved.