react-native-palette

A React-Native library which extracts prominent colors from an image. On Android, it wraps the Android Pallete Class. On iOS, it uses code from react-native-color-grabber.

An example app is included.

Getting started

$ npm install react-native-palette --save

Mostly automatic installation for Android and iOS

$ react-native link react-native-palette

Manual installation

Android

1. Open up android/app/src/main/java/[...]/MainApplication.java

• Add import io.palette.RNPalettePackage; to the imports at the top of the file
• Add new RNPalettePackage() to the list returned by the getPackages() method

2. Append the following lines to android/settings.gradle:

 include ':react-native-palette'
 project(':react-native-palette').projectDir = new File(rootProject.projectDir, '../node_modules/react-native-palette/android')

3. Insert the following lines inside the dependencies block in android/app/build.gradle:

   compile project(':react-native-palette')

iOS

1. Add node_modules/react-native-palette/ios/RNPalette.xcodeproj to your Xcode project

API

getAllSwatches(options, image, (error, swatches) => {})

options

An object containing option properties. There are two properties and they're valid for iOS only. On Android, this parameter is ignored.

Property	Type	Info
threshold	Float	Determines whether white or black text will be selected to contrast with the selected color. It is the value for L, in the complex formula at the end of this StackOverflow comment. The default value is 0.179.
quality	String	One of "low", "medium", or "high". Higher quality extracts more colors, takes more time and consumes more memory. Default is "low".

image

A path to an image such as that returned by react-native-image-picker. For iOS use the origURL field of the image picker response, because only images from assets-library:// have been tested. For Android use the path field.

callback

The callback is passed an error parameter and an array of swatches representing the dominant colors in the image. Typically 16 swatches are returned on Android, fewer on iOS.

getNamedSwatches(image, (error, swatches) => {})

Android only.

image

Same as in getAllSwatches

swatches

An object keyed by the qualities of colors defined by the Android Palette Class. The keys are the following:

• "Vibrant"
• "Vibrant Dark"
• "Vibrant Light"
• "Muted"
• "Muted Dark"
• "Muted Light"

The values are swatches (possibly null) or with the fields defined below.

Swatch Fields

Colors include alpha in the react-native rgba(255,255,255,1.0) format. Note that on iOS10 devices UIExtendedSRGBColorSpace color values may be greater than 255 or less than 0, but they will render correctly on the device.

Field	Info
color	The main color of the swatch.
population	The dominance of this swatch in the image. You can sort on this field to find the most dominant swatch. Android: A positive integer. iOS: A floating point number between 0 and 1.
titleTextColor	A text color which contrasts well with the main swatch color for use in titles.
bodyTextColor	A text color which contrasts well with the main swatch color for use as body text.
swatchInfo	A string encapsulating all the above and more. Can be used for debugging. Android: Note that the hex strings are in the format #aarrggbb rather than the react-native format. iOS: the result string returned by the old (react-native-color-grabber) API.

Example

  import {getAllSwatches} from 'react-native-palette';
  import ImagePicker from 'react-native-image-picker'

  ImagePicker.launchImageLibrary({}, (response)  => {
    var path =  Platform.OS === 'ios' ? response.origURL : response.path;
    getAllSwatches({}, path, (error, swatches) => {
      if (error) {
        console.log(error);
      } else {
        swatches.sort((a, b) => {
          return b.population - a.population;
        });
        swatches.forEach((swatch) => {
          console.log(swatch.swatchInfo);
        });
      }
    });
  });