/**  
* 老紫竹，模仿谷歌地图制作的图片缩放，拖动的效果js  
* www.laozizhu.com  
* 部分功能不能再Firefox下面用，有点可惜  
*/  
var widthFrame = 800;   
var heightFrame = 500;   
var widthMax;   
var heightMax;   
var widthMap;   
var heightMap;   
var map;   
var mapLayer;   
var centerX;   
var centerY;   
var mousex;   
var mousey;   
function init(m,ml){   
  map = m;     
  map.onmousemove = mouseMove;   
  mapLayer = ml;   
  widthMax = map.width;   
  heightMax = map.height;   
  widthMap = map.width;   
  heightMap = map.height;   
  centerX = widthMap/2;   
  centerY = heightMap/2;   
  toCenter();   
}   
function showParam(){   
  document.getElementById("widthMax").innerText=widthMax;   
  document.getElementById("heightMax").innerText=heightMax;   
  document.getElementById("widthMap").innerText=widthMap;   
  document.getElementById("heightMap").innerText=heightMap;   
  document.getElementById("centerX").innerText=centerX;   
  document.getElementById("centerY").innerText=centerY;   
  document.getElementById("mousex").innerText=mousex;   
  document.getElementById("mousey").innerText=mousey;   
}   
function toCenter(){   
  if(centerX< widthFrame/2){   
    centerX = widthFrame/2;   
  }   
  if(centerX>widthMap-widthFrame/2){   
    centerX = widthMap-widthFrame/2;   
  }   
  if(centerY< heightFrame/2){   
    centerY = heightFrame/2;   
  }   
  if(centerY> heightMap-heightFrame/2){   
    centerY = heightMap-heightFrame/2;   
  }   
  showParam();   
  mapLayer.style.left=-1*(centerX-widthFrame/2)+"px";   
  mapLayer.style.top=-1*(centerY-heightFrame/2)+"px";   
}   
function resizeTo(w,h){   
  widthMap = map.width = w;   
  heightMap = map.height = h;   
  toCenter();   
}   
function bigger(){   
  var w = widthMap*1.2;   
  if(w>widthMax){   
    w= widthMax;   
  }     
     
  var h = heightMap*1.2;   
  if(h>heightMax){   
    h = heightMax;   
  }   
  centerX = centerX*w/widthMap;   
  centerY = centerY*h/heightMap;   
  resizeTo(w,h);   
}   
function smaller(){   
  var w = widthMap*0.8;   
  var h = heightMap*0.8;   
  // 保证不会缩小到屏幕放不下了   
  if(w<widthFrame){   
    w = widthFrame;   
    h = heightMax*w/widthMax; // 保证缩放比例   
  }else if(h<heightFrame){   
    h = heightFrame;   
    w = widthMax*h/heightMax; // 保证缩放比例   
  }   
  centerX = centerX*w/widthMap;   
  centerY = centerY*h/heightMap;   
  resizeTo(w,h);   
}   
function doRightClick(){   
  var x = mousex-300;   
  var y = mousey-100;   
  if(x>widthFrame/2+50){   
    centerX+=20;   
  }else if(x<widthFrame/2-50){   
    centerX-=20;   
  }   
  if(y>heightFrame/2+50){   
    centerY += 20;       
  }else if(y<heightFrame/2-50){   
    centerY -=20;   
  }   
  toCenter();   
}   
function moveButton(x,y){   
  if(x==0 && y==0){   
    centerX = widthMap/2;   
    centerY = heightMap/2;   
  }else{   
    centerX += x;   
    centerY += y;   
  }   
  toCenter();   
}   
function mouseMove(ev){   
  ev = ev || window.event;   
  var mousePos = mouseCoords(ev);   
  mousex = mousePos.x;   
  mousey = mousePos.y;   
    //判断鼠标已被按下且onmouseover和onmousedown事件发生在同一对象上   
  if(down&&event.srcElement==obj){   
    centerX -= (mousex-x)*1;   
    centerY -= (mousey-y)*1;   
    toCenter();   
    x = mousex;   
    y = mousey;   
  }   
  showParam();   
}   
function mouseCoords(ev){   
  if(ev.pageX || ev.pageY){   
    return {x:ev.pageX, y:ev.pageY};   
  }   
  return {   
    x:ev.clientX + document.body.scrollLeft - document.body.clientLeft,   
    y:ev.clientY + document.body.scrollTop - document.body.clientTop   
  };   
}   
// 鼠标拖动效果   
var x,y,z,down=false,obj;    
function initMouseDrag(ev){   
  ev = ev || window.event;   
  obj=ev.srcElement       //事件触发对象   
  obj.setCapture()              //设置属于当前对象的鼠标捕捉   
  z=obj.style.zIndex            //获取对象的z轴坐标值   
  //设置对象的z轴坐标值为100，确保当前层显示在最前面   
  obj.style.zIndex=100   
  x=mousex     //获取鼠标指针位置相对于触发事件的对象的X坐标   
  y=mousey     //获取鼠标指针位置相对于触发事件的对象的Y坐标   
  down=true           //布尔值，判断鼠标是否已按下，true为按下，false为未按下   
  obj.style.cursor='move';   
}   
function moveit(){   
}    
function stopdrag(){   
  //onmouseup事件触发时说明鼠标已经松开，所以设置down变量值为false   
  down=false     
  obj.style.zIndex=z         //还原对象的Z轴坐标值   
  obj.releaseCapture() //释放当前对象的鼠标捕捉   
  obj.style.cursor='normal';   
}    
var scrolling = false;   
function scrollIt(){   
  if(scrolling){   
    return true;   
  }   
  scrolling = true;   
  if(event.wheelDelta>0){   
    bigger();   
  }else{   
    smaller();   
  }     
  scrolling = false;   
  event.returnValue = false;   
}