// JavaScript Document

var coef = 0.01 ; // avancement de l'opacité
var temps = 20 ; // temps entre chaque changement d'opacité
var temps_pause = 1000 ; // temps d'attente entre 2 changements d'images
var nombre_image = 14 ; // nombre d'images a faire bouger
var prefix_image = '../images/header/header-'; // chemin + prefix du nom des images
var suffix_image = '.png' ; // suffix + '.extension' du nom des images
// pas touche
var indice = 2; // les 2 premiere image sont deja charger dans le HTML, on commence a la 3eme
var isIE = navigator.userAgent.toLowerCase().indexOf('msie')!=-1 ;
var isMoz = navigator.userAgent.toLowerCase().indexOf('moz')!=-1 ;
var browser;
var img1 = null;
var img2 = null ;
var sens = 1;
var tabImg; // tab contenant les images

function prechargerImg()
{	
	tabImg = new Array( nombre_image );
	for( i = 0 ; i <= nombre_image - 1 ; i++ )
	{
		tabImg[i]=new Image();
		tabImg[i].src = prefix_image+(i+1)+suffix_image;
	}
}

function header_init()
{
	img1 = document.getElementById( "img-header_img1" ) ;
	img2 = document.getElementById( "img-header_img2" ) ;
	if( isIE )
		browser = "Navigateur: Internet Explorer";
	else
	if( isMoz )
		browser = "Navigateur: Mozilla (FireFox)";
	else
		browser = "Navigateur: Autre";
		
	prechargerImg();
	change_opacity();
}

function change_opacity()
{
var opacity1 = 0 ;
var opacity2 = 0 ;

//	document.getElementById( 'div-bottom_msg' ).innerHTML = 'change_opacity called';
	
	if( isIE ) // for IE
	{ 
		opacity1 = parseFloat( img1.filters.alpha.opacity );
		opacity2 = parseFloat( img2.filters.alpha.opacity );
	}
	else if( isMoz )// for mozilla
	{ 
		opacity1 = parseFloat( img1.style.opacity );
		opacity2 = parseFloat( img2.style.opacity );
	}
	else
	{
		opacity1 = parseFloat( img1.style.opacity );
		opacity2 = parseFloat( img2.style.opacity );
	}
	
	if( sens )
	{
		if( isIE ) // for IE
		{ 
			img1.filters.alpha.opacity = opacity1 + coef * 100;
			img2.filters.alpha.opacity = opacity2 - coef * 100;
		}
		else if( isMoz ) // for Mozilla
		{ 
			img1.style.opacity = opacity1 + coef;
			img2.style.opacity = opacity2 - coef;
		}
		else
		{
			img1.style.opacity = opacity1 + coef;
			img2.style.opacity = opacity2 - coef;
		}
	}
	else
	{
		if( isIE ) // for IE
		{ 
			img1.filters.alpha.opacity = opacity1 - coef * 100;
			img2.filters.alpha.opacity = opacity2 + coef * 100;
		}
		else if( isMoz ) // for Mozilla
		{
			img1.style.opacity = opacity1 - coef;
			img2.style.opacity = opacity2 + coef;
		}
		else
		{
			img1.style.opacity = opacity1 - coef;
			img2.style.opacity = opacity2 + coef;
		}
	}
	if( isIE ) // for IE
	{ 
		opacity1 = parseFloat( img1.filters.alpha.opacity );
		opacity2 = parseFloat( img2.filters.alpha.opacity );
	}
	else if( isMoz ) // for mozilla
	{ 
		opacity1 = parseFloat( img1.style.opacity );
		opacity2 = parseFloat( img2.style.opacity );
	}
	else
	{
		opacity1 = parseFloat( img1.style.opacity );
		opacity2 = parseFloat( img2.style.opacity );
	}
	
	opacity1 = opacity1.toFixed(2);
	opacity2 = opacity2.toFixed(2);
//	document.getElementById( 'div-bottom_msg' ).innerHTML = browser + ' -> '+' opacity1:'+opacity1+' opacity2:'+opacity2;
	
	// on fait varier le sens d'opacité du bazar
	if( opacity2 <= 0.01 )
	{ 
		img2.src=tabImg[ indice++ ].src;
		sens = 0;
		if( indice == ( tabImg.length )) 
			indice=0;
//		document.getElementById( 'div-bottom_msg' ).innerHTML = browser + ' -> ' + ' pause...';
		window.setTimeout( "change_opacity()", temps_pause ) ; // attente
		return 0;
	} else
	if( opacity1 <= 0.01 )
	{ 
		img1.src=tabImg[ indice++ ].src;
		sens = 1;
		if( indice == ( tabImg.length )) 
			indice=0;
//		document.getElementById( 'div-bottom_msg' ).innerHTML = browser + ' -> ' + ' pause...';
		window.setTimeout( "change_opacity()", temps_pause ) ; // attente
		return 0;
	}
	
	// document.getElementById( 'div-bottom_msg' ).innerHTML = browser + ' -> '+' opacity1:'+opacity1+' opacity2:'+opacity2+' coef:'+coef;
	
	window.setTimeout( "change_opacity()", temps ) ;
}