134 lines
4.3 KiB
Markdown
134 lines
4.3 KiB
Markdown
# jpeg-js
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A pure javascript JPEG encoder and decoder for node.js
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[](http://travis-ci.org/eugeneware/jpeg-js)
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## Installation
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This module is installed via npm:
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``` bash
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$ npm install jpeg-js
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```
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## Example Usage
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### Decoding JPEGs
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Will decode a buffer or typed array into a `Buffer`;
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``` js
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var jpeg = require('jpeg-js');
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var jpegData = fs.readFileSync('grumpycat.jpg');
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var rawImageData = jpeg.decode(jpegData);
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console.log(jpegData.data);
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/*
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{ width: 320,
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height: 180,
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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 ... > }
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*/
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```
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To decode directly into a `Uint8Array`, pass `true` as the second argument to
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`decode`:
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``` js
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var jpeg = require('jpeg-js');
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var jpegData = fs.readFileSync('grumpycat.jpg');
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var rawImageData = jpeg.decode(jpegData, true); // return as Uint8Array
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console.log(jpegData.data);
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/*
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{ width: 320,
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height: 180,
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data: { '0': 91, '1': 64, ... } } // typed array
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*/
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```
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### Encoding JPEGs
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``` js
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var jpeg = require('jpeg-js');
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var width = 320, height = 180;
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var frameData = new Buffer(width * height * 4);
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var i = 0;
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while (i < frameData.length) {
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frameData[i++] = 0xFF; // red
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frameData[i++] = 0x00; // green
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frameData[i++] = 0x00; // blue
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frameData[i++] = 0xFF; // alpha - ignored in JPEGs
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}
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var rawImageData = {
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data: frameData,
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width: width,
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height: height
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};
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var jpegImageData = jpeg.encode(rawImageData, 50);
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console.log(jpegImageData);
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/*
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<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 ... >
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*/
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```
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## License
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### Decoding
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This library builds on the work of two other JPEG javascript libraries,
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namely [jpgjs](https://github.com/notmasteryet/jpgjs) for the decoding
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which is licensed under the Apache 2.0 License below:
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Copyright 2011 notmasteryet
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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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[http://www.apache.org/licenses/LICENSE-2.0](http://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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### Encoding
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The encoding is based off a port of the JPEG encoder in [as3corelib](https://code.google.com/p/as3corelib/source/browse/trunk/src/com/adobe/images/JPGEncoder.as).
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The port to Javascript was done by by Andreas Ritter, www.bytestrom.eu, 11/2009.
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The Adobe License for the encoder is:
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**Adobe**
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Copyright (c) 2008, Adobe Systems Incorporated
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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met:
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* Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of Adobe Systems Incorporated nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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