我写了一个上传服务器前制作缩略图的函数,请大家看看

/**
 * Created by IntelliJ IDEA.
 * author: dean
 * Date: 2006-8-14
 * Time: 10:45:39
 * description: 支持比例缩放，限制比例。
 *                        主要目的为在上传图片到服务器端之前进行预览。
 *                        当然更可用在HTTP形式路径的图片上。
 *  location: mapbar.com
 */

function ThumbnailTool() {

    this.width = 0;
    this.height = 0;
    this.maxPixel = 50;
    this.boolean = false;
    this.src = "";

    this.setMaxPixel = function (maxPixel) {
        this.maxPixel = maxPixel;
    }

    this.isAutoMaxSize = function (bToMaxSize) {
        this.bToMaxSize = bToMaxSize;
    }

    this.getWidth = function () {
        return this.width;
    }

    this.getHeight = function () {
        return this.height;
    }

    this.getSrc = function () {
        return this.src;
    }

    this.toThumbnail = function (imgSrc) {

        var img = new Image();
        img.src = imgSrc;
        var imgWidht = img.width;
        var imgHeight = img.height;
        this.src = img.src;

        if (!(this.width > 0 && this.height > 0)) {
            if (imgWidht >= imgHeight) {
                if (imgWidht > this.maxPixel || this.bToMaxSize) {
                    this.height = parseInt(parseFloat(imgHeight) / parseFloat(imgWidht) * this.maxPixel + 0.5);
                    this.width = this.maxPixel;
                } else {
                    this.width = imgWidht;
                    this.height = imgHeight;
                }
            } else {
                if (imgHeight > this.maxPixel || this.bToMaxSize) {
                    this.width = parseInt(parseFloat(imgWidht) / parseFloat(imgHeight) * this.maxPixel + 0.5);
                    this.height = this.maxPixel;
                } else {
                    this.width = imgWidht;
                    this.height = imgHeight;
                }
            }
        }
    }
}

调用方法：

     var tbImg = new ThumbnailTool();

     //解决有时候尺寸太大的图片没有读入内存时出现的问题imgSrc 可以是本地路径也可以是http方式的路径
     while(tbImg.getWidth()<2 || tbImg.getHeight()<2 ){
         tbImg.setMaxPixel(50);
         tbImg.toThumbnail(imgSrc);
    //   tbImg.isAutoMaxSize (true);
     }

     document.getElementById("d9").width = tbImg.getWidth();
     document.getElementById("d9").height = tbImg.getHeight();
     document.getElementById("d9").src = tbImg.getSrc();
     document.getElementById("d9").alt = "";

疑问:
    怎么能把读入内存时出现的问题的解决方法放到函数里啊?