使用canvas 图片加载异步变成同步代码

 function loadImg(_url, _this) {
            var img = new Image();
            img.src = _url;
            img.onload = function () {
                cxt.drawImage(img, 0, 0)
                //把canvas作为纹理
                var texture = new THREE.Texture(canvas);
                texture.needsUpdate = true;
                var spritematerial = new THREE.SpriteMaterial({ map: texture });
                var sprite = new THREE.Sprite(spritematerial);
                //进行缩放
                sprite.scale.set(20, 10, 20);
                sprite.position.set(coorArr[0], coorArr[1], coorArr[2])
                _this.props.scene.add(sprite);
            };
        }
        loadImg(wsp, this);

图片加载完成之后 在场景中添加图片