three.js 将图片马赛克化

initCanvas() {
    canvas = document.createElement('canvas');
    content = canvas.getContext('2d');
    canvas.width = 1600;
    canvas.height = 1200;
    img = new Image();
    img.crossOrigin = '*';
    img.src = "/static/images/base/girl.jpg";
    img.onload = () => {
        content.drawImage(img, 0, 0, canvas.width, canvas.height);
        imgDate = content.getImageData(0, 0, canvas.width, canvas.height);
        this.createPotCloud();   //创建点云
    };
}

createPotCloud() {
    if (points) {
        scene.remove(points)
    }
    let cw = Math.floor(canvas.width / size);
    let ch = Math.floor(canvas.height / size);
    particles = cw * ch;
    geometry = new THREE.BufferGeometry();
    positions = new Float32Array(Math.floor(particles * 3));
    positions_af = new Float32Array(Math.floor(particles * 3));
    var colors = new Float32Array(Math.floor(particles * 3));
    for (var i = 0; i < positions.length; i += 1) {

        positions[3 * i] = - canvas.width / 2 + (i % cw) * size;
        positions[3 * i + 1] = canvas.height / 2 + Math.floor((-1 - i) / cw) * size;
        positions[3 * i + 2] = 0;

        let selectPos = size * (i % cw) + Math.floor(i / cw) * cw * size * size;
        colors[3 * i] = imgDate.data[4 * selectPos] / 255.0;
        colors[3 * i + 1] = imgDate.data[4 * selectPos + 1] / 255.0;
        colors[3 * i + 2] = imgDate.data[4 * selectPos + 2] / 255.0;
    }
    geometry.setAttribute('position', new THREE.BufferAttribute(positions, 3));
    geometry.setAttribute('color', new THREE.BufferAttribute(colors, 3))
    geometry.dynamic = true;
    geometry.attributes.position.needsUpdate = true;
    var material = new THREE.PointsMaterial({ size: size, vertexColors: THREE.VertexColors })
    points = new THREE.Points(geometry, material);
    points.name = 'points';
    scene.add(points);
    loaded = true;
},