//图片比例缩放控制 www.zixuephp.com

function DrawImage(ImgD,FitWidth,FitHeight){ 
    var image=new Image(); 
    image.src=ImgD.src; 
    if(image.width>0 && image.height>0) 
    { 
        if(image.width/image.height>= FitWidth/FitHeight) 
        { 
            if(image.width>FitWidth) 
            { 
                ImgD.width=FitWidth; 
                ImgD.height=(image.height*FitWidth)/image.width; 
            } 
            else 
            { 
                ImgD.width=image.width;   
                ImgD.height=image.height;   
            } 
        } 
        else 
        { 
           if(image.height>FitHeight) 
           { 
                ImgD.height=FitHeight; 
                ImgD.width=(image.width*FitHeight)/image.height; 
           } 
           else 
           { 
                ImgD.width=image.width; 
                ImgD.height=image.height; 
            } 
        }   
    } 
}

实例如下：

<div class="type-file-preview">

<img src="<?php echo UPLOAD_SITE_URL."/".ATTACH_ADV."/".$pic;?>" onload="javascript:DrawImage(this,500,500);">

</div>