jpeg-js

A pure javascript JPEG encoder and decoder for node.js

NOTE: this is a synchronous (i.e. CPU-blocking) library that is much slower than native alternatives. If you don't need a pure javascript implementation, consider using async alternatives like sharp in node or the Canvas API in the browser.

Installation

This module is installed via npm:

1$ npm install jpeg-js

Example Usage

Decoding JPEGs

Will decode a buffer or typed array into a Buffer;

1var jpeg = require('jpeg-js');
2var jpegData = fs.readFileSync('grumpycat.jpg');
3var rawImageData = jpeg.decode(jpegData);
4console.log(rawImageData);
5/*
6{ width: 320,
7  height: 180,
8  data: <Buffer 5b 40 29 ff 59 3e 29 ff 54 3c 26 ff 55 3a 27 ff 5a 3e 2f ff 5c 3c 31 ff 58 35 2d ff 5b 36 2f ff 55 35 32 ff 5a 3a 37 ff 54 36 32 ff 4b 32 2c ff 4b 36 ... > }
9*/

To decode directly into a Uint8Array, pass useTArray: true in options decode:

1var jpeg = require('jpeg-js');
2var jpegData = fs.readFileSync('grumpycat.jpg');
3var rawImageData = jpeg.decode(jpegData, {useTArray: true}); // return as Uint8Array
4console.log(rawImageData);
5/*
6{ width: 320,
7  height: 180,
8  data: { '0': 91, '1': 64, ... } } // typed array
9*/

Decode Options

Option	Description	Default
colorTransform	Transform alternate colorspaces like YCbCr. undefined means respect the default behavior encoded in metadata.	undefined
useTArray	Decode pixels into a typed Uint8Array instead of a Buffer.	false
formatAsRGBA	Decode pixels into RGBA vs. RGB.	true
tolerantDecoding	Be more tolerant when encountering technically invalid JPEGs.	true
maxResolutionInMP	The maximum resolution image that jpeg-js should attempt to decode in megapixels. Images larger than this resolution will throw an error instead of decoding.	100
maxMemoryUsageInMB	The (approximate) maximum memory that jpeg-js should allocate while attempting to decode the image in mebibyte. Images requiring more memory than this will throw an error instead of decoding.	512

Encoding JPEGs

1var jpeg = require('jpeg-js');
2var width = 320,
3  height = 180;
4var frameData = new Buffer(width * height * 4);
5var i = 0;
6while (i < frameData.length) {
7  frameData[i++] = 0xff; // red
8  frameData[i++] = 0x00; // green
9  frameData[i++] = 0x00; // blue
10  frameData[i++] = 0xff; // alpha - ignored in JPEGs
11}
12var rawImageData = {
13  data: frameData,
14  width: width,
15  height: height,
16};
17var jpegImageData = jpeg.encode(rawImageData, 50);
18console.log(jpegImageData);
19/*
20{ width: 320,
21  height: 180,
22  data: <Buffer 5b 40 29 ff 59 3e 29 ff 54 3c 26 ff 55 3a 27 ff 5a 3e 2f ff 5c 3c 31 ff 58 35 2d ff 5b 36 2f ff 55 35 32 ff 5a 3a 37 ff 54 36 32 ff 4b 32 2c ff 4b 36 ... > }
23*/
24// write to file
25fs.writeFileSync('image.jpg', jpegImageData.data);

License

Decoding

This library builds on the work of two other JPEG javascript libraries, namely jpgjs for the decoding which is licensed under the Apache 2.0 License below:

Copyright 2011 notmasteryet

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.

Encoding

The encoding is based off a port of the JPEG encoder in as3corelib.

The port to Javascript was done by by Andreas Ritter, www.bytestrom.eu, 11/2009.

The Adobe License for the encoder is:

Adobe

Copyright (c) 2008, Adobe Systems Incorporated All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

• Neither the name of Adobe Systems Incorporated nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Contributing

jpeg-js is an OPEN Open Source Project. This means that:

Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.

See the CONTRIBUTING.md file for more details.

Contributors

jpeg-js is only possible due to the excellent work of the following contributors:

Adobe	GitHub/adobe
Yury Delendik	GitHub/notmasteryet
Eugene Ware	GitHub/eugeneware
Michael Kelly	GitHub/mrkelly
Peter Liljenberg	GitHub/petli
XadillaX	GitHub/XadillaX
strandedcity	GitHub/strandedcity
wmossman	GitHub/wmossman
Patrick Hulce	GitHub/patrickhulce
Ben Wiley	GitHub/benwiley4000