写一个方法获取图片的原始宽高

Answer 1

    function loadImageAsync(url) {
        return new Promise(function(resolve, reject) {
            var image = new Image();

            image.onload = function() {
                var obj = {
                    w: image.naturalWidth,
                    h: image.naturalHeight
                }
                resolve(obj);
            };

            image.onerror = function() {
                reject(new Error('Could not load image at ' + url));
            };
            image.src = url;
        });
    }