node-vibrant

node-vibrant

Extract prominent colors from an image.

Update Notes

• Some major refactor/rewriting comes with node-vibrant@2.0.0:

  • Closely matches latest Android M Palette API with new features such as Builder and Filter
  • Optimization: ~4x speed-up over original implementation
  • Implement image downsampling for both node.js and browsers
  • More stream-lined design
  • Better test coverage for both node.js and browser environment

• node-vibrant@1.x is a node.js port of Vibrant.js, which is a javascript port of the awesome Palette class in the Android support library.

Features

• Identical (asynchronous) API for both node.js and browser environment
• Support browserify
• Consistent results (*See Result Consistency)

Install

$ npm install node-vibrant

Usage

node.js / browserify

# Use in node.js or bundle with browserify
Vibrant = require('node-vibrant')

# Using builder
Vibrant.from('path/to/image').getPalette (err, palette) ->
    console.log palette

# Using constructor
v = new Vibrant('path/to/image', opts)
v.getPalette (err, palette) ->
  console.log(swatches)

Browser

<!-- Debug version -->
<script src="/path/to/dist/vibrant.js"></script>
<!-- Uglified version -->
<script src="/path/to/dist/vibrant.min.js"></script>

<script>
  // Use `Vibrant` in script
  // Vibrant is exported to global. window.Vibrant === Vibrant
  Vibrant.from('path/to/image').getPalette(function(err, palette) {});
  // Or
  var v = new Vibrant('/path/to/image', opts);
  // ... same as in node.js
</script>

Contribution Guidelines

1. Make changes
2. Write test specs if necessary
3. Pass tests
4. Commit source files only (without compiled files)

References

Vibrant

Main class of node-vibrant.

Vibrant.from(image)

Make a Builder for an image. Returns a Builder instance.

Name	Type	Description
image	string or Buffer(node.js only)	Path to image file (support HTTP/HTTPs)

constructor(image, opts)

Name	Type	Description
image	string or Buffer(node.js only)	Path to image file (support HTTP/HTTPs)
opts	object	Options (optional)

opts

Field	Default	Description
colorCount	64	amount of colors in initial palette from which the swatches will be generated
quality	5	Scale down factor used in downsampling stage. 1 means no downsampling. If maxDimension is set, this value will not be used.
generator	Vibrant.Generator.Default	An Generator instance
maxDimension	undefined	The max size of the image's longer side used in downsampling stage. This field will override quality.
filters	[]	An array of filters
Image	Image.Node or Image.Browser	An Image implementation class
Quantizer	Vibrant.Quantizer.NoCopy	A Quantizer implementation class

getPalette(cb)

Name	Type	Description
cb	function	callback function

cb(err, palette)

Name	Type	Description
err	object	Error (if thrown)
palette	Array<Swatch>	Resulting swatches

getSwatches(cb)

Alias of getPalette.

Vibrant.Builder

Helper class for change configurations and create a Vibrant instance. Methods of a Builder instance can be chained like:

Vibrant.form(src)
  .quality(1)
  .clearFilters()
  # ...
  getPalette (err, palette) ->

constructor(src, opts)

Arguments are the same as Vibrant.constructor.

quality(q)

Sets opts.quality to q. Returns this Builder instance.

maxColorCount(n)

Sets opts.colorCount to n. Returns this Builder instance.

maxDimension(d)

Sets opts.maxDimension to d. Returns this Builder instance.

addFilter(f)

Adds a filter function. Returns this Builder instance.

removeFilter(f)

Removes a filter function. Returns this Builder instance.

clearFilters()

Clear all filters. Returns this Builder instance.

useImage(image)

Specifies which Image implementation class to use. Returns this Builder instance.

useQuantizer(quantizer)

Specifies which Quantizer implementation class to use. Returns this Builder instance.

useGenerator(generator)

Sets opts.generator to generator. Returns this Builder instance.

build()

Builds and returns a Vibrant instance as configured.

getPalette(cb)

Builds a Vibrant instance as configured and calls its getPalette method.

getSwatches(cb)

Alias of getPalette.

Vibrant.Swatch

Represents a color swatch generated from an image's palette.

constructor(rgb, population)

Internal use.

Name	Type	Description
rgb	Array<Number>	[r, g, b]
population	Number	Population of the color in an image

getHsl()

getPopulation()

getRgb()

getHex()

getTitleTextColor()

Returns an appropriate color to use for any 'body' text which is displayed over this Swatch's color.

getBodyTextColor()

Returns an appropriate color to use for any 'title' text which is displayed over this Swatch's color.

Vibrant.Util

Utility methods. Internal usage.

clone(o)

Make a deep copy of o.

defaults()

Same as underscore.js's defaults. Re-implemented to reduce browserify package size.

hexToRgb(hex)

rgbToHex(r, g, b)

hslToRgb(h, s, l)

rgbToHsl(r, g, b)

xyzToRgb(x, y, z)

rgbToXyz(r, g, b)

xyzToCIELab(x, y, z)

rgbToCIELab(l, a, b)

deltaE94(lab1, lab2)

Computes CIE delta E 1994 diff between lab1 and lab2. The 2 colors are in CIE-Lab color space. Used in tests to compare 2 colors' perceptual similarity.

rgbDiff(rgb1, rgb2)

Compute CIE delta E 1994 diff between rgb1 and rgb2.

hexDiff(hex1, hex2)

Compute CIE delta E 1994 diff between hex1 and hex2.

getColorDiffStatus(d)

Gets a string to describe the meaning of the color diff. Used in tests.

Delta E	Perception	Returns
<= 1.0	Not perceptible by human eyes.	"Perfect"
1 - 2	Perceptible through close observation.	"Close"
2 - 10	Perceptible at a glance.	"Good"
11 - 49	Colors are more similar than opposite	"Similar"
50 - 100	Colors are exact opposite	Wrong

Vibrant.Filter

A collection of built-in filters.

Filter(r, g, b, a): function<boolean>

A Filter provides a mechanism for exercising fine-grained control over which colors are valid within a resulting. It takes color's rgba value and returns true if the color is allowed.

Filter.Default

Keeps the original vibrant.js's filtering behavior as reference.

Vibrant.Quantizer

Base class of a Quantizer.

Quantizer.MMCQ

Default quantizer. ~4x faster than baseline quantizer. (Rewritten version of NoCopy)

Quantizer.NoCopy

Optimized quantizer. ~4x faster than baseline quantizer.

Quantizer.Baseline

Original vibrant.js quantizer. Used for tests and benchmarks only. It does not support downsampling nor filters.

Vibrant.Generator

Base class for Generator.

Generator.Default

Default Generator implementation.

constructor(opts)

opts

Field	Default	Description
targetDarkLuma	0.26	target luma value for generating the dark swatches, values should be in the range [0 1]
maxDarkLuma	0.45	maximal luma threshold for generating the dark swatches, values should be in the range [0 1]
minLightLuma	0.55	minimal luma threshold for generating the light swatches, values should be in the range [0 1]
targetLightLuma	0.74	target luma value for generating the light swatches, values should be in the range [0 1]
minNormalLuma	0.3	minimal luma threshold for generating the Vibrant and Muted swatches, values should be in the range [0 1]
targetNormalLuma	0.5	target luma value for generating the Vibrant and Muted swatches, values should be in the range [0 1]
maxNormalLuma	0.7	maximal luma threshold for generating the Vibrant and Muted swatches, values should be in the range [0 1]
targetMutedSaturation	0.3	target saturation for generating the Muted swatch, values should be in the range [0 1]
maxMutesSaturation	0.4	maximal saturation threshold for generating the Muted swatches, values should be in the range [0 1]
targetVibrantSaturation	1.0	target saturation value for generating the Vibrant swatches, values should be in the range [0 1]
minVibrantSaturation	0.35	minimal saturation threshold for generating the Vibrant swatches, values should be in the range [0 1]
weightSaturation	3	saturation weight coefficient for determining each swatch, actual impact depends on other weights
weightLuma	6	luma weight coefficient for determining each swatch, actual impact depends on other weights
weightPopulation	1	population weight coefficient for determining each swatch, actual impact depends on other weights

Gulp Tasks

Task	Description
detaul	[coffee, browser]
coffee	Compile node.js target
browser	Compile broser target (browserify)
benchmark	Runs benchmarks
test	Runs node.js test specs
browser-test	Runs browser test specs (with karma)

Notes

Intentional Deviation From vibrant.js

• node-vibrant takes image path, not the image object as parameter for the obvious reason that node.js environment has no access to HTML DOM object.
• node-vibrant provides asynchronous API since most node.js image processing library is asynchronous. And the original vibrant.js workflow is asynchronous any way (though you will have to handle the image loading yourself, while node-vibrant does it for you).
• node-vibrant uses one single opts object to hold all options for future expansions. And it feels more node.js-like.
• node-vibrant uses method call to initiate image processing instead of constructor so that developers can use it with Promise.

Result Consistency

The results is consistent within each user's browser instance regardelss of visible region or display size of the image, unlike the original vibrant.js implementation.

However, due to the very nature of HTML5 canvas element, image rendering is platform/machine-dependent. Thus the resulting swatches in browser environment varies and may not be the same as in node.js nor in another machine. See Canvas Fingerprinting.

The test specs use CIE delta E 1994 color difference to measure inconsistencies across platforms. It compares the generated color on node.js, Chrome, Firefox and IE11. At quality == 1 (no downsampling) and no filters, the results are rather consistent. Color diffs between browsers are mostly not perceptible by human eyes. Downsampling will cause perceptible inconsistent results across browsers due to differences in canvas implementations.