konva/lib/filters/Contrast.js

<p align="center"> <img src="https://konvajs.org/android-chrome-192x192.png" alt="Konva logo" height="180" /> </p>

import { Factory } from '../Factory.js';
import { Node } from '../Node.js';
import { getNumberValidator } from '../Validators.js';
export const Contrast = function (imageData) {
    var adjust = Math.pow((this.contrast() + 100) / 100, 2);
    var data = imageData.data, nPixels = data.length, red = 150, green = 150, blue = 150, i;
    for (i = 0; i < nPixels; i += 4) {
        red = data[i];
        green = data[i + 1];
        blue = data[i + 2];
        red /= 255;
        red -= 0.5;
        red *= adjust;
        red += 0.5;
        red *= 255;
        green /= 255;
        green -= 0.5;
        green *= adjust;
        green += 0.5;
        green *= 255;
        blue /= 255;
        blue -= 0.5;
        blue *= adjust;
        blue += 0.5;
        blue *= 255;
        red = red < 0 ? 0 : red > 255 ? 255 : red;
        green = green < 0 ? 0 : green > 255 ? 255 : green;
        blue = blue < 0 ? 0 : blue > 255 ? 255 : blue;
        data[i] = red;
        data[i + 1] = green;
        data[i + 2] = blue;
    }
};
Factory.addGetterSetter(Node, 'contrast', 0, getNumberValidator(), Factory.afterSetFilter);