voluptasquisquam/src/image/compute/__tests__/colorHistogram.js

Image processing and manipulation in JavaScript

import {Image} from 'test/common';
import 'should';

describe('calculate the colorHistogram', function () {
    it('check getColorHistogram method', function () {
        let image = new Image(1, 2, [0, 0, 0, 255, 255, 255, 255, 255]);

        let histogram = image.getColorHistogram({useAlpha: false, nbSlots: 8});
        Array.from(histogram).should.eql([1, 0, 0, 0, 0, 0, 0, 1]);

        histogram = image.getColorHistogram({useAlpha: true, nbSlots: 8});
        Array.from(histogram).should.eql([1, 0, 0, 0, 0, 0, 0, 1]);

        (function () {
            image.getColorHistogram({nbSlots: 3});
        }).should.throw(/nbSlots must be a power of 8/);
    });

    it('check getColorHistogram method with transparency', function () {
        let image = new Image(1, 2, [0, 0, 0, 255, 255, 255, 255, 0]);

        let histogram = image.getColorHistogram({useAlpha: false, nbSlots: 8});
        Array.from(histogram).should.eql([1, 0, 0, 0, 0, 0, 0, 1]);

        histogram = image.getColorHistogram({useAlpha: true, nbSlots: 8});
        Array.from(histogram).should.eql([1, 0, 0, 0, 0, 0, 0, 0]);
    });

    it('check getColorHistogram property with transparency', function () {
        let image = new Image(1, 4, [0, 0, 0, 255, 255, 255, 255, 0, 0, 0, 0, 255, 255, 255, 255, 255]);

        let histogram = image.colorHistogram;
        Array.from(histogram).length.should.equal(512);
        Array.from(histogram)[0].should.equal(2);
        Array.from(histogram)[511].should.equal(1);
    });
});