PC版改为mobile版遇到了点问题

[tomorrow93]

以下是图片拖动插件，PC是没问题的，现要改成移动端版该怎么改啊，JS菜鸟好多都看不懂只能来求救了！

<div class="ldxx-img" id="ldxx-img"> <!-- 容器 -->
	<div class="shapan" draggable="false" id="img"> <!-- 拖动的是这里 -->
		<img src="images/banner.jpg"> <!-- 图片不限制大小 -->
	</div>
</div>

//图片拖动
    window.onload = function(){
        var draging = false, lastPoint;
        var body = document.body;
        var img = document.getElementById('img');
        img.onmousedown = function(e){
            e = e || window.event;
            var x = e.clientX;
            var y = e.clientY;
            if(!lastPoint){
                lastPoint = {};
            }
            lastPoint.x = x;
            lastPoint.y = y;
            draging = true;
            if(e.preventDefault){
                e.preventDefault();
            }else{
                return false;
            }
        }
        img.ondragstart = function(e){
            e = e || window.event;
            if(e.preventDefault){
                e.preventDefault();
            }else{
                return false;
            }
        }
        img.onmouseup = function(){
            draging = false;
            lastPoint = undefined;
        }
        if(document.addEventListener){
            body.addEventListener('mousemove',function(e){
                onMouseMove(e);
            },false);
            body.addEventListener('mouseup',onMouseUp,false);
        }else{
            body.attachEvent('onmousemove',function(){
                var event = window.event;
                onMouseMove(event);
            })
            body.attachEvent('onmouseup',onMouseUp);
        }

        function onMouseMove(e){
            if(!draging){
                return;
            }
            var img = document.getElementById('img');
			var ldxx_img = document.getElementById('ldxx-img');
            if(lastPoint){
                var x = e.clientX , y = e.clientY;
                var imgTop = parseFloat(img.style.top || '0');
                var imgLeft = parseFloat(img.style.left || '0');
                var changeX = x - lastPoint.x , changeY = y - lastPoint.y;
				var dis_X = imgLeft + changeX;
				var dis_Y = imgTop + changeY;
				var sub_img = img.getElementsByTagName('img')[0];
				var sub_img_width = sub_img.offsetWidth;
				var sub_img_height = sub_img.offsetHeight;
				var img_width = ldxx_img.offsetWidth;
				var img_height = ldxx_img.offsetHeight;
				var dis_w = img_width -  sub_img_width;
				var dis_h = img_height - sub_img_height;
				if(dis_X>0){
					dis_X = 0;
				}
				if(dis_X < dis_w){
					dis_X = dis_w;
				}
				
				if(dis_Y>0){
					dis_Y = 0;
				}
				if(dis_Y < dis_h){
					dis_Y = dis_h;
				}
				
                img.style.top = dis_Y + 'px';
                img.style.left = dis_X + 'px';
                lastPoint.x = x, lastPoint.y = y;
            }
        }
        function onMouseUp(){
            draging = false;
            lastPoint = undefined;
        }
    }

[tomorrow93]

csdn的代码高亮有问题，我在重新贴一下js代码 //图片拖动 window.onload = function(){ var draging = false, lastPoint; var body = document.body; var img = document.getElementById('img'); img.onmousedown = function(e){ e = e || window.event; var x = e.clientX; var y = e.clientY; if(!lastPoint){ lastPoint = {}; } lastPoint.x = x; lastPoint.y = y; draging = true; if(e.preventDefault){ e.preventDefault(); }else{ return false; } } img.ondragstart = function(e){ e = e || window.event; if(e.preventDefault){ e.preventDefault(); }else{ return false; } } img.onmouseup = function(){ draging = false; lastPoint = undefined; } if(document.addEventListener){ body.addEventListener('mousemove',function(e){ onMouseMove(e); },false); body.addEventListener('mouseup',onMouseUp,false); }else{ body.attachEvent('onmousemove',function(){ var event = window.event; onMouseMove(event); }) body.attachEvent('onmouseup',onMouseUp); } function onMouseMove(e){ if(!draging){ return; } var img = document.getElementById('img'); var ldxx_img = document.getElementById('ldxx-img'); if(lastPoint){ var x = e.clientX , y = e.clientY; var imgTop = parseFloat(img.style.top || '0'); var imgLeft = parseFloat(img.style.left || '0'); var changeX = x - lastPoint.x , changeY = y - lastPoint.y; var dis_X = imgLeft + changeX; var dis_Y = imgTop + changeY; var sub_img = img.getElementsByTagName('img')[0]; var sub_img_width = sub_img.offsetWidth; var sub_img_height = sub_img.offsetHeight; var img_width = ldxx_img.offsetWidth; var img_height = ldxx_img.offsetHeight; var dis_w = img_width - sub_img_width; var dis_h = img_height - sub_img_height; if(dis_X>0){ dis_X = 0; } if(dis_X < dis_w){ dis_X = dis_w; } if(dis_Y>0){ dis_Y = 0; } if(dis_Y < dis_h){ dis_Y = dis_h; } img.style.top = dis_Y + 'px'; img.style.left = dis_X + 'px'; lastPoint.x = x, lastPoint.y = y; } } function onMouseUp(){ draging = false; lastPoint = undefined; } }