//基本設定
var headerImgBoxName = "headerImgBox";//ヘッダーイメージボックス名
var headerImgName = "headerImg"; //ヘッダーイメージ名
var browsSeconds = 10;//イメージがステイしている時間（秒）
var opacityGrade = 5;//フェードの段階（100まで）
var imgOpacity = 100;
var imgNum = 0;
var photos = new Array(
	"http://birth-rock.com/photo/122.jpg",
	"http://birth-rock.com/photo/01.jpg",
	"http://birth-rock.com/photo/02.jpg",
	"http://birth-rock.com/photo/03.jpg",
	"http://birth-rock.com/photo/04.jpg",
	"http://birth-rock.com/photo/05.jpg",
	"http://birth-rock.com/photo/06.jpg",
	"http://birth-rock.com/photo/07.jpg"
);

//配列のランダム入れ替え
function changeArray(list){
  var i = list.length;
  while (--i) {
    var j = Math.floor(Math.random() * (i + 1));
    if (i == j) continue;
    var k = list[i];
    list[i] = list[j];
    list[j] = k;
  }
  return list;
}

//最初のイメージを決定
function headerRotate() {
	changeArray(photos);
	document.write('<img id="headerImg" width="605" height="300" alt="Photo Gallery" src="' +photos[imgNum] + '" />');
}

//ヘッダーイメージアニメーション
function headerAnimation() {
	var imgObj = document.getElementById(headerImgName);
	document.getElementById(headerImgBoxName).style.backgroundImage = 'url(' + photos[imgNum] + ')';
	imgFade();
}

//フェード
function imgFade() {
	var imgObj = document.getElementById(headerImgName);
	if (imgOpacity <= opacityGrade) {//フェード外
		imgOpacity = 100;
		imgSelect();
		setTimeout("imgFade()",browsSeconds*300);
	}else{//フェード中
		imgOpacity -= opacityGrade;
		setOpacity(imgObj,imgOpacity);
		setTimeout("imgFade()",100);
	}
}

//次イメージ選択
function imgSelect() {
	var divObj = document.getElementById(headerImgBoxName);
	var imgObj = document.getElementById(headerImgName);
	imgObj.src = photos[imgNum];
	setOpacity(imgObj,100);
	if(imgNum == photos.length-1){
		imgNum = 0;
	}else{
		imgNum++;
	}
	divObj.style.backgroundImage = 'url(' + photos[imgNum] + ')';
}

//不透明度設定
function setOpacity(obj, opacity) {
	opacity = (opacity == 100)?100:opacity;
	obj.style.filter = "alpha(opacity:"+opacity+")";	
	obj.style.KHTMLOpacity = opacity/100;
	obj.style.MozOpacity = opacity/100;
	obj.style.opacity = opacity/100;
}

window.onload = headerAnimation;