js图片等比例缩放

<script language="JavaScript" type="text/javascript">

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;

             }

        }

     }

}

script>

<img src="asfds.jpg" />

<img src="asfds.jpg" alt="自动缩放后的效果"  onload="javascript:DrawImage(this,300,200);" />

 

原图：

效果图：