specs/gradientfill.test.js

const pureimage = require('pureimage')
const fs = require('fs')
describe('drawing gradients',() => {

    let image
    let c
    const WHITE = 0xFFFFFFFF
    const BLACK = 0x000000FF

    beforeEach(()=>{
        image = pureimage.make(20,20)
        c = image.getContext('2d')
        c.fillStyle = 'black'
        c.fillRect(0,0,200,200)
    })


    it('is making a linear gradient',(done)=>{
        const grad = c.createLinearGradient(0,0,20,20)
        grad.addColorStop(0,'white')
        grad.addColorStop(1,'blue')
        c.fillStyle = grad
        c.fillRect(0,0,20,20)

        pureimage.encodePNGToStream(image, fs.createWriteStream('lgrad.png')).then(() => {
            console.log('wrote out lgrad.png')
            expect(image.getPixelRGBA(0, 0)).toBe(0xFFFFFFFF)
            expect(image.getPixelRGBA(19, 19)).toBe(0x0C0CFFFF)
            done()
        })
    })

    it('is making a radial gradient',(done)=>{
        const grad = c.createRadialGradient(10,10, 5, 10,10,10)
        grad.addColorStop(0,'white')
        grad.addColorStop(1,'green')
        c.fillStyle = grad
        c.fillRect(0,0,20,20)

        pureimage.encodePNGToStream(image, fs.createWriteStream('rgrad.png')).then(() => {
            console.log('wrote out rgrad.png')
            expect(image.getPixelRGBA(0, 0)).toBe(0x00FF00FF)
            expect(image.getPixelRGBA(10, 10)).toBe(0xFFFFFFFF)
            done()
        })
    })
});