voluptasquisquam/src/image/filter/invert.js

Image processing and manipulation in JavaScript

// we try the faster methods

import {validateArrayOfChannels} from '../../util/channel';

/**
 * Invert an image. The image
 * @memberof Image
 * @instance
 * @param {object} options
 * @param {(undefined|number|string|[number]|[string])} [options.channels=undefined] Specify which channels should be processed
 *      * undefined : we take all the channels but alpha
 *      * number : this specific channel
 *      * string : converted to a channel based on rgb, cmyk, hsl or hsv (one letter code)
 *      * [number] : array of channels as numbers
 *      * [string] : array of channels as one letter string
 * @return {this}
 */
export default function invert(options = {}) {
    let {channels} = options;

    this.checkProcessable('invertOneLoop', {
        bitDepth: [1, 8, 16]
    });

    if (this.bitDepth === 1) {
        // we simply invert all the integers value
        // there could be a small mistake if the number of points
        // is not a multiple of 8 but it is not important
        let data = this.data;
        for (let i = 0; i < data.length; i++) {
            data[i] = ~data[i];
        }
    } else {
        channels = validateArrayOfChannels(this, {channels});

        for (let c = 0; c < channels.length; c++) {
            let j = channels[c];
            for (let i = j; i < this.data.length; i += this.channels) {
                this.data[i] = this.maxValue - this.data[i];
            }
        }
    }

    return this;
}