示例代码：

<div id="div_content">

    <img src="http://static.cnblogs.com/images/logo_small.gif" alt="Alternate Text" />

</div>

<script type="text/javascript">

    $(document).ready(function () {

        var myimg;

        var maxwidth = 643;

        $("#div_content img").load(function () {

            for (i = 0; i < $(this).length; i++) {

                myimg = $(this)[i];

                if (myimg.width > maxwidth) {

                    myimg.width = maxwidth;

                }

            }

        });

    });

</script>

参考资料：

• JavaScript获取图片的原始尺寸
• jquery .each() .load() wait for completion
• jQuery .load inside .each