javascript自动适应图片大小

博客来源 http://blog.csdn.net/eduxh/article/details/1906246

//图片自适应大小
//id为img控件的id
//width与height为img父控件的宽高——即img的最大宽高
//示例：<img id="dd" src="ee.jpg" onload="imgFit('dd',100,200)" />"
function imgFit(id,width,height)
{
    var imageArr=document.getElementById(id);
    if(imageArr.offsetWidth>width || imageArr.offsetHeight>height)
    {
        imageRate1=parseInt(imageArr.offsetWidth)/width;
        imageRate2=parseInt(imageArr.offsetHeight)/height;
        if(imageRate2>imageRate1)
            imageArr.style.height = imageArr.offsetHeight/imageRate2+"px";
        else
            imageArr.style.width = imageArr.offsetWidth/imageRate1 +"px";
    }
}
添加居中处理：

function imgFit(imageArr,width,height)
{
    //var imageArr=document.getElementById(id);
    //if(imageArr.offsetWidth>width || imageArr.offsetHeight>height)
    //{
    //alert(imageArr.style.marginTop);
        sWidth=imageArr.offsetWidth;
        sHeight=imageArr.offsetHeight;
        imageRate1=parseInt(imageArr.offsetWidth)/width;
        imageRate2=parseInt(imageArr.offsetHeight)/height;
        if(imageRate2>imageRate1)
        {
            imageArr.style.height = sHeight/imageRate2+"px";
            imageArr.style.marginLeft=(width-sWidth/imageRate2)/2+"px";
        }
        else
        {
            imageArr.style.width = sWidth/imageRate1 +"px";
            imageArr.style.marginTop=(height-sHeight/imageRate1)/2+"px";
        }   
        //alert(imageArr.offsetWidth+":"+imageArr.offsetHeight);
    //}
}