图像的等比例缩放

<script type="text/javascript"> 
        $(function() { 
            $("#originalWidth").val($("#img1").width()); 
            $("#originalHeight").val($("#img1").height()); 
            var originalWidth = $("#originalWidth").val(); 
            var originalHeight = $("#originalHeight").val(); 
            var desireWidth = $("#desireWidth").val(); 
            var desireHeight = $("#desireHeight").val(); 
            var scaledWidth = 0, scaledHeight = 0; 
            var wRate = 1, hRate = 1, setRate = 1; 
            $("#btn").click(function() { 

                if (originalHeight > desireHeight) { 
                    hRate = desireHeight / originalHeight; 
                } 
                if (originalWidth > desireWidth) { 
                    wRate = desireWidth / originalWidth; 
                } 

                if (wRate != 1 || hRate != 1) { 
                    if (wRate > hRate) { 
                        setRate = hRate; 
                    } 
                    else { 
                        setRate = wRate; 
                    } 
                } 
                scaledWidth = originalWidth * setRate; 
                scaledHeight = originalHeight * setRate; 
                $("#scaledWidth").val(scaledWidth); 
                $("#scaledHeight").val(scaledHeight); 
                $("#img1").width(scaledWidth); 
                $("#img1").height(scaledHeight); 
            }); 

        }); 
    </script>