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trim-image-data

💇‍♀️ Function for trimming/cropping transparent pixels surrounding an image. Very similar to trim-canvas, but accepts and returns an ImageData-instance instead. Also allows specifying custom colors to trim.

Demo

https://trim-image-data.netlify.app

Usage

import trimImageData from 'trim-image-data';

// trim surrounding fully transparent pixels
const trimmedTransparent = trimImageData(imageData);

// trim surrounding white pixels
const trimmedWhite = trimImageData(imageData, {
  trimColor: ([red, green, blue, alpha]) => {
    return red === 255 && green === 255 && blue === 255 && alpha === 255;
  };
});

// supports passing a RGBA array instead of a callback too
const trimmedWhite = trimImageData(imageData, {
  trimColor: [255, 255, 255, 255]
});

// trim any pixel with max alpha
const trimmedDim = trimImageData(imageData, {
  trimColor: ([alpha]) => alpha === 255
});

Installation

# npm
npm install trim-image-data

# yarn
yarn add trim-image-data

# pnpm
pnpm add trim-image-data

API

trimImageData(imageData, trimOptions)

Creates a trimmed version of an ImageData-instance. Trims fully transparent pixels by default. Does not mutate the recieved instance.

Parameters:

  • imageData - the ImageData-instance to crop

  • trimOptions - optional

    • trimColor([red, green, blue, alpha]) => boolean | trimColor: [r, g, b, a]
      Callback function used to determine if a value should be trimmed or not. Receives an object of RGBA channels and should return a boolean.

      Also accepts a single RGBA-array as a shorthand for a callback that returns true if all channels are equal to the corresponding channel in the array.

Return value:

A new, trimmed ImageData-instance.

getTrimEdges(imageData, trimOptions)

Calculates the number of pixels to trim from each side of an image, provided as an ImageData object. Does not actually trim the image.

Uses the same options and defaults as trimImageData.

Parameters:

  • imageData - the ImageData-instance to calculate the trim for

  • trimOptions - optional

    • trimColor([red, green, blue, alpha]) => boolean | trimColor: [r, g, b, a]
      Callback function used to determine if a value should be trimmed or not. Receives an object of RGBA channels and should return a boolean.

      Also accepts a single RGBA-array as a shorthand for a callback that returns true if all channels are equal to the corresponding channel in the array.

Return value:

A new, trimmed ImageData-instance.

Related packages

  • crop-image-data - crops ImageData by specified number of pixels. Used as a dependency in trim-image-data.

Credits

A lot of the code in this repo is based on trim-canvas, I just had a need for the same functionality without passing a canvas.