Replace Color

replace-color replaces color with another one pixel by pixel. Especially this will be helpful if you want to remove the watermarks from the images. This package is built on top of Jimp.

Install

npm install --save replace-color

Basic usage

replace-color supports both Node.js error-first callbacks and promises. The package returns a Jimp’s instance which you can use to execute some other image manipulations methods or save it with Jimp’s write method.

Node.js error-first callback example

const replaceColor = require('replace-color')
replaceColor({
  image: './input.jpg',
  colors: {
    type: 'hex',
    targetColor: '#FF0000',
    replaceColor: '#FFFFFF'
  }
}, (err, jimpObject) => {
  if (err) return console.log(err)
  jimpObject.write('./output.jpg', (err) => {
    if (err) return console.log(err)
  })
})

Promise example

const replaceColor = require('replace-color')
replaceColor({
  image: './input.jpg',
  colors: {
    type: 'hex',
    targetColor: '#FF0000',
    replaceColor: '#FFFFFF'
  }
})
  .then((jimpObject) => {
    jimpObject.write('./output.jpg', (err) => {
      if (err) return console.log(err)
    })
  })
  .catch((err) => {
    console.log(err)
  })

API

replaceColor(options, [callback])

• options Object (required) - the options.
  • image Buffer | Object | String (required) - an image being processed. It can be a buffer, Jimp’s instance, a path to an image on your host machine or a URL address to an image on the internet. Please, take a look at the tests to understand all these options.
  • colors Object (required) - the colors.
    • type String (required) - a targetColor and replaceColor type. Supported values are hex and rgb.
    • targetColor String | Array (required) - a color you want to replace. A 7-symbol string in case of hex type (e.g. #000000, #FFFFFF). An array of 3 integers from 0 to 255 in case of rgb type (e.g. [0, 0, 0], [255, 255, 255]).
    • replaceColor String | Array (required) - a new color which will be used instead of a targetColor color. A 7-symbol string in case of hex type (e.g. #000000, #FFFFFF). An array of 3 integers from 0 to 255 in case of rgb type (e.g. [0, 0, 0], [255, 255, 255]). You can also define a transparent channel for a replaceColor color. To achieve this, you can use a 9-symbol string in case of hex type (e.g. #00000000, #FFFFFFFF). Based on this Stack Overflow answer, an alpha channel is controlled by the first pair of digits in a hex code (e.g., 00 means fully transparent, 7F means 50%, FF means fully opaque). Also, you can use an array of 4 integers in case of rgb type. The first 3 integers must be from 0 to 255 and the last one must be from 0 to 1 (e.g., 0 means fully transparent, 0.5 means 50%, 1 means fully opaque).
  • formula String (optional) - one of the three formulas to calculate the color difference. Supported values are E76, E94 and E00. The default value is E00 (the best algorithm).
  • deltaE Number (optional) - a deltaE value which corresponds to a JND. The default value is 2.3. Please, read more about deltaE here. Generaly speaking, if the processed by the replace-color package image still has the watermarks, you should increase the deltaE value.
• callback Function (optional) - a Node.js error-first callback.

Examples

Remove a watermark

Let’s try to remove a watermark from this picture.

const replaceColor = require('replace-color')
replaceColor({
  image: 'https://i.imgur.com/XqNTuzp.jpg',
  colors: {
    type: 'hex',
    targetColor: '#FFB3B7',
    replaceColor: '#FFFFFF'
  },
  deltaE: 20
})
  .then((jimpObject) => {
    jimpObject.write('./output.jpg', (err) => {
      if (err) return console.log(err)
    })
  })
  .catch((err) => {
    console.log(err)
  })

Result

Change a background color from a green to a blue one

Let’s try to change a background color for this picture.

const replaceColor = require('replace-color')
replaceColor({
  image: 'https://i.imgur.com/aCxZpaq.png',
  colors: {
    type: 'hex',
    targetColor: '#66AE74',
    replaceColor: '#63A4FF'
  },
  deltaE: 10
})
  .then((jimpObject) => {
    jimpObject.write('./output.png', (err) => {
      if (err) return console.log(err)
    })
  })
  .catch((err) => {
    console.log(err)
  })

Result

Change a background color from a green to a transparent one (using hex type)

Let’s try to change a background color for this picture.

const replaceColor = require('replace-color')
replaceColor({
  image: 'https://i.imgur.com/aCxZpaq.png',
  colors: {
    type: 'hex',
    targetColor: '#66AE74',
    replaceColor: '#00000000'
  },
  deltaE: 10
})
  .then((jimpObject) => {
    jimpObject.write('./output.png', (err) => {
      if (err) return console.log(err)
    })
  })
  .catch((err) => {
    console.log(err)
  })

Result

Change a background color from a green to a 50% transparent green (using rgb type)

Let’s try to change a background color for this picture.

const replaceColor = require('replace-color')
replaceColor({
  image: 'https://i.imgur.com/aCxZpaq.png',
  colors: {
    type: 'rgb',
    targetColor: [102, 174, 116],
    replaceColor: [102, 174, 116, 0.5]
  },
  deltaE: 10
})
  .then((jimpObject) => {
    jimpObject.write('./output.png', (err) => {
      if (err) return console.log(err)
    })
  })
  .catch((err) => {
    console.log(err)
  })

Result

Error handling

To indicate the replace-color‘s errors you should use the err instanceof replaceColor.ReplaceColorError class.

replaceColor({}, (err, jimpObject) => {
  if (err instanceof replaceColor.ReplaceColorError) {
    //  A replace-color's error occurred. 
  } else if (err) {
    // An unknown error occurred.
  }
  // Everything went fine.
})

A replace-color‘s error instance has the code and field properties. For now, the package has two codes: PARAMETER_INVALID and PARAMETER_REQUIRED. The field property shows which exact property was not passed or is invalid using the glob notation (e.g. options.colors.type). Please, take a look at the tests to see all the possible cases.

License

MIT