colour-extractor-fixed

colour-extractor-fixed

(This is a working version of josip's node-colour-extractor)

Extract colour palettes from photos using Node.js.

Before Installing

Download and Install ImageMagick here

NOTE: Windows users should check installation options as shown here.

For run-time issues, you can refer to this one.

Installation

$ npm i -g gm
$ npm i colour-extractor-fixed --save

NOTE: colour-extractor-fixed depends on gm module, which in turn depends on GraphicsMagick.

Sample

Usage

colour-extractor-fixed exports two functions:

ce = require('colour-extractor-fixed')
ce.topColours('Photos/Cats/01.jpg', true, function (colours) {
  console.log(colours);
});

topColours function takes three arguments:

• path to your photo,
• true if you'd like the resulting array to be sorted by frequency, false if you'd like to get colours sorted as they appear in the photo (top-to-bottom),
• a callback function.

Callback function will be passed an Array with RGB triplet of each colour and its frequency:

[
  [1,   [46, 70, 118]],
  [0.3, [0,   0,   2]],
  [0.2, [12,  44,  11]]
]

The second function, colourKey, returns an array with nine colours, where each one can be mapped to a 3x3 box, ie. super-pixelised representation of the photo.

ce.colourKey('Photos/Cats/999999.jpg', function (colours) {
  database.store('colour-keys', photoId, colours);
  res.send(colours);
  // render colours to user while they wait for the photo to load.
  // (or something equally brilliant)
});

Utilities

colour-extractor-fixed exports two more utility functions:

> ce.rgb2hex(100, 10, 12);
'#640a0c'
> ce.rgb2hex([44, 44, 44]);
'#2c2c2c'
> ce.hex2rgb('#ffffff');
[255, 255, 255]
> ce.hex2rgb('45c092')
[69, 192, 146]

How does it work?

That's what I'd like to know as well! Anyhow, colour-extractor-fixed parses GraphicMagick's histogram, tries to detect similar colours and remove ones which appear less frequently than others.

If you happen to know an actual algorithm that deals with this sort of stuff, don't hesitate to contact me!

License

colour-extractor-fixed is published under MMIT license, please see the LICENSE file for full details.

Photos used in the sample can be downloaded from Flickr:

• Title?
• nel profondo del blu
• Reykjavík revisited