react-native-grayscale

A super lightweight react native package that converts an image passed as a base64 string to a base64 string that represents the grayscale version of that image.

:exclamation: Available for iOS only.

:exclamation: Tested on react-native>=0.60 only.

Support for android coming soon.

Installation

$ yarn add react-native-grayscale

or

$ npm install react-native-grayscale --save

then,

$ cd ios

$ pod install

done.

Specs

...

import getBase64Grayscale from "react-native-grayscale"

...

getBase64Grayscale(base64)

| Parameters | Required | Type | Description | | ---------- | -------- | ------ | ------------------------------------------------------------------------------------- | | base64 | required | string | the base64 string of the image. The prefix data:image/[format];base64, is optional. |

:exclamation: Note that if the base64 is without a prefix data:image/[format];base64, setting the uri property of the source prop at Image will result in the image NOT beeing displayed.

| Returns | Description | | ----------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Promise<> | Returns a promise that will resolve with the base64 string of the grayscale version of the image or will be rejected with an error if the input base64 image is in incorrect format |

Example

import React, { useEffect, useState } from "react";
import getBase64Grayscale from "react-native-grayscale";
import { Image, View } from "react-native";

const Test = props => {
  const base64Icon =
    "data:image/png;base64,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";

  const [grayscaleBase64Img, setGrayscaleBase64Img] = useState("");

  useEffect(() => {
    const toGrayscale = async () => {
      const grayscale = await getBase64Grayscale(base64Icon);
      setGrayscaleBase64Img(grayscale);
    };
    toGrayscale();
  }, []);

  return (
    <View>
      <Image
        style={{
          width: 100,
          height: 50,
          borderWidth: 1,
          borderColor: "black"
        }}
        source={{ uri: base64Icon }}
      />
      <Image
        style={{
          width: 100,
          height: 50,
          borderWidth: 1,
          borderColor: "black"
        }}
        source={{ uri: `data:image/png;base64,${grayscaleBase64Img}` }}
      />
    </View>
  );
};