voluptasquisquam/src/image/transform/__tests__/cropAlpha.js

Image processing and manipulation in JavaScript

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

describe('cropAlpha transform', function () {
    it('grey + alpha - no crop', function () {
        const image = new Image(3, 4, [
            1, 255, 2, 255, 3, 255,
            4, 255, 5, 255, 6, 255,
            7, 255, 8, 255, 9, 255,
            10, 255, 11, 255, 12, 255
        ], {kind: 'GREYA'});

        const cropped = image.cropAlpha();
        cropped.width.should.equal(image.width);
        cropped.height.should.equal(image.height);
        Array.from(cropped.data).should.eql(Array.from(image.data));
    });

    it('grey + alpha - some crop', function () {
        const image = new Image(3, 4, [
            1, 0, 2, 255, 3, 255,
            4, 0, 5, 255, 6, 255,
            7, 0, 8, 255, 9, 255,
            10, 0, 11, 0, 12, 0
        ], {kind: 'GREYA'});

        const cropped = image.cropAlpha();
        cropped.width.should.equal(2);
        cropped.height.should.equal(3);
        Array.from(cropped.data).should.eql([
            2, 255, 3, 255,
            5, 255, 6, 255,
            8, 255, 9, 255,
        ]);
    });

    it('grey + alpha - only one remains', function () {
        const image = new Image(3, 4, [
            1, 0, 2, 0, 3, 0,
            4, 0, 5, 255, 6, 0,
            7, 0, 8, 0, 9, 0,
            10, 0, 11, 0, 12, 0
        ], {kind: 'GREYA'});

        const cropped = image.cropAlpha();
        cropped.width.should.equal(1);
        cropped.height.should.equal(1);
        Array.from(cropped.data).should.eql([5, 255]);
    });

    it('grey + alpha - with threshold', function () {
        const image = new Image(3, 4, [
            1, 0, 2, 240, 3, 0,
            4, 110, 5, 255, 6, 250,
            7, 110, 8, 239, 9, 250,
            10, 10, 11, 0, 12, 90
        ], {kind: 'GREYA'});

        const cropped = image.cropAlpha({threshold: 240});
        cropped.width.should.equal(2);
        cropped.height.should.equal(3);
        Array.from(cropped.data).should.eql([
            2, 240, 3, 0,
            5, 255, 6, 250,
            8, 239, 9, 250,
        ]);
    });

    it('grey + alpha - error high threshold', function () {
        const image = new Image(3, 4, [
            1, 40, 2, 240, 3, 50,
            4, 110, 5, 0, 6, 250,
            7, 110, 8, 239, 9, 250,
            10, 10, 11, 0, 12, 90
        ], {kind: 'GREYA'});


        (function () {
            image.cropAlpha();
        }).should.throw(/Could not find new dimensions. Threshold may be too high./);

    });
});