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color-transform

Streaming image color space transforms

Installation

npm install color-transform

Example

var ColorTransform = require('color-transform');

// Convert a buffer (list of supported transforms below)
var rgb = ColorTransform.cmyk2rgb(new Buffer([ 0, 56, 128, 32 ]))
// => new Buffer([ 1, 13, 20 ])

// Streaming example. Converts a CMYK JPEG to an RGB PNG
fs.createReadStream('cmyk.jpg')
  .pipe(new JPEGDecoder)
  .pipe(new ColorTransform('rgb'))
  .pipe(new PNGEncoder)
  .pipe(fs.createWriteStream('out.png'));

Supported color spaces

color-transform supports transforms between the following color spaces. The only exception is CMYK, which is currently only supported in one direction - you can convert from CMYK to any of the other color spaces, but not to CMYK.

  • 'rgb' - standard RGB
  • 'rgba' - RGB with alpha
  • 'gray' - grayspace
  • 'graya' - grayspace with alpha
  • 'cmyk' - CMYK

API

You can call the conversion functions directly with a buffer to convert, as shown in the example. The functions are named by joining the two color spaces with a 2, such as rgb2gray, and cmyk2rgb.

You can also use the streaming API, which is a pixel-stream. The constructor accepts two parameters: source color space, and destination color space. If you pipe another pixel-stream into color-transform, the source color space is optional in the constructor since it will be learned from the source stream.

You don't need to worry about writing to the stream in whole pixel chunks. The ColorTransform stream will automatically buffer if there is a chunk boundary in the middle of a pixel.

// create a stream that converts from cmyk to rgb
var s = new ColorTransform('cmyk', 'rgb');

// pipe a stream that happens to be cmyk to an rgb color transform.
fs.createReadStream('cmyk.jpg')
  .pipe(new JPEGDecoder)
  .pipe(new ColorTransform('rgb'))
  // ...

License

MIT

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Streaming image color space transforms

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