function zjistiVelikostOkna() {
  var myWidth = 0, myHeight = 0;
  if( typeof( window.innerWidth ) == 'number' ) {
    //Non-IE
    myWidth = parent.window.innerWidth;
    myHeight = parent.window.innerHeight;
  } else if( parent.document.documentElement && ( parent.document.documentElement.clientWidth || parent.document.documentElement.clientHeight ) ) {
    //IE 6+ in 'standards compliant mode'
    //myWidth = parent.document.documentElement.clientWidth;
    //myHeight = parent.ocument.documentElement.clientHeight;
        myWidth = parent.document.body.clientWidth;
    myHeight = parent.document.body.clientHeight;
  } else if( parent.document.body && ( parent.document.body.clientWidth || parent.document.body.clientHeight ) ) {
    //IE 4 compatible
    myWidth = parent.document.body.clientWidth;
    myHeight = parent.document.body.clientHeight;
  }
  return [ myWidth, myHeight ];
}

function scrollXY() {
  var X = 0, Y = 0;
  if( typeof( parent.pageYOffset ) == 'number' ) {
    Y = parent.pageYOffset;
    X = parent.pageXOffset;
  } else if( parent.document.body && ( parent.document.body.scrollLeft || parent.document.body.scrollTop ) ) {
    Y = parent.document.body.scrollTop;
    X = parent.document.body.scrollLeft;
  } else if( parent.document.documentElement && ( parent.document.documentElement.scrollLeft || parent.document.documentElement.scrollTop ) ) {
    Y = parent.document.documentElement.scrollTop;
    X = parent.document.documentElement.scrollLeft;
  }
  return [ X, Y ];
}

function endObr() {                                         
  var hlavni = document.getElementById("obrHlavni");
  var pozadi = document.getElementById("obrPozadi");
  hlavni.style.display = "none";
  pozadi.style.display = "none";
  document.body.style.overflow = "auto";
}

function heightPlocha() {
  if( window.innerHeight && window.scrollMaxY ) { // FIREFOX
    pageWidth = window.innerWidth + window.scrollMaxX;
    pageHeight = window.innerHeight + window.scrollMaxY;
  } else if ( document.body.scrollHeight > document.body.offsetHeight ) {  // EXPLORER
    pageWidth = document.body.scrollWidth;
    pageHeight = document.body.scrollHeight;
  } else {
    pageWidth = document.body.offsetWidth + document.body.offsetLeft; 
    pageHeight = document.body.offsetHeight + document.body.offsetTop; 
  }
  return [ pageHeight, pageWidth ];
}
   
function zobrObr(height,width,cesta,obrazek,kolikata)
{  
   var zadost = new XMLHttpRequest();    

       if (zadost) 
       { 
          var pozadi = document.getElementById("obrPozadi");
          var hlavni = document.getElementById("obrHlavni");
          var imgobr = document.getElementById("imgobr");
          document.body.style.overflow = "hidden";
          hlavni.innerHTML = "načítám obrázek...";
          
          zadost.onreadystatechange = function k()
                                  {
                                      var sirka_vyska=zjistiVelikostOkna();
                                      var horlevy=scrollXY();
                                      
                                      if (width > 750) {
                                          width = width/1.3;
                                      }
                                      if (height > 500) {
                                          height = height/1.3;
                                      }
                                      
                                      var top = horlevy[1]+Math.round(sirka_vyska[1]/2)-Math.round((height)/2);
                                      var left = horlevy[0]+Math.round(sirka_vyska[0]/2)-Math.round((width)/2);
                                      var stranka=heightPlocha();

                                  if (zadost.readyState == 4 && zadost.status == 200) 
                                  {
                                      if (zadost.responseText != "") 
                                      {  
                                          hlavni.innerHTML = zadost.responseText;
                                          document.getElementById("imgobr").height = Math.round(height);
                                          document.getElementById("imgobr").width = Math.round(width);
                                          hlavni.style.top = top+ "px";
                                          hlavni.style.left = left+ "px";
                                          hlavni.style.display = "block";
                                          pozadi.style.display = "block";
                                          pozadi.style.height = stranka[0]+ "px";
                                          pozadi.style.width = stranka[1]+ "px";
                                      }
                                 }
                                 }
               

          zadost.open('GET', 'zobr_foto.php?cesta='+cesta+'&obr='+obrazek+'&kolikata='+kolikata);
          zadost.send(null);       
        }
        else
       {
           alert('Bohuzel ale Vas prohlizec nepodporuje XMLHttpRequest() :(');
       }  
}