timerID = null;

so = 'none';

function degradadoInicializar() {
		if(typeof document.images["imagenGrande"].filters == 'object')
		{
			so = (document.images["imagenGrande"].filters.length > 0 && typeof document.images["imagenGrande"].filters.alpha == 'object' && typeof document.images["imagenGrande"].filters.alpha.opacity == 'number') ? 'ie' : 'none';
		}
		else if(typeof document.images["imagenGrande"].style.opacity != 'undefined')
		{
			so = 'w3c';
		}
		else if(typeof document.images["imagenGrande"].style.MozOpacity != 'undefined')
		{
			so = 'moz';
		}
		else
		{
			so = 'none';
		}
}

function degradadoFinalizar() {
	if(document.getElementById){
		clearTimeout(timerID);
	}
}

function degradado( ) {
    	if(document.getElementById){
			switch(so)
			{
				case 'ie' :
					if( document.images["imagenGrande"].filters.alpha.opacity < 99 ) {
						document.images["imagenGrande"].filters.alpha.opacity = parseInt(document.images["imagenGrande"].filters.alpha.opacity)+11;
    					timerID = setTimeout("degradado()",32);
    				}
    				else {
    					degradadoFinalizar();
    				}
					break;

				case 'w3c' :
    				if( document.images["imagenGrande"].style.opacity < 0.99 ) {
						document.images["imagenGrande"].style.opacity = parseFloat(document.images["imagenGrande"].style.opacity)+0.11;
    					timerID = setTimeout("degradado()",32);
    				}
    				else {
    					degradadoFinalizar();
    				}
    				break;

				case 'moz' :
    				if( document.images["imagenGrande"].style.MozOpacity < 0.99 ) {
						document.images["imagenGrande"].style.MozOpacity = parseFloat(document.images["imagenGrande"].style.MozOpacity)+0.11;
    					timerID = setTimeout("degradado()",32);
    				}
    				else {
    					degradadoFinalizar();
    				}
					break;

				default:
					break;
			}
    	}
}

function degradadoInverso( ) {
    	if(document.getElementById){
			switch(so)
			{
				case 'ie' :
					if( document.images["imagenGrande"].filters.alpha.opacity > 0 ) {
						document.images["imagenGrande"].filters.alpha.opacity = parseInt(document.images["imagenGrande"].filters.alpha.opacity)-11;
    					timerID = setTimeout("degradadoInverso()",32);
    				}
    				else {
    					degradadoFinalizar();
    				}
					break;

				case 'w3c' :
    				if( document.images["imagenGrande"].style.opacity > 0 ) {
						document.images["imagenGrande"].style.opacity = parseFloat(document.images["imagenGrande"].style.opacity)-0.11;
    					timerID = setTimeout("degradadoInverso()",32);
    				}
    				else {
    					degradadoFinalizar();
    				}
    				break;

				case 'moz' :
    				if( document.images["imagenGrande"].style.MozOpacity > 0 ) {
						document.images["imagenGrande"].style.MozOpacity = parseFloat(document.images["imagenGrande"].style.MozOpacity)-0.11;
    					timerID = setTimeout("degradadoInverso()",32);
    				}
    				else {
    					degradadoFinalizar();
    				}
					break;

				default:
					break;
			}
    	}
}

function cambiarImagen( rutaImagen, tituloImagen ) {
    	cambiarTituloImagen(tituloImagen);
		degradadoInicializar();
		degradadoFinalizar();
    	document.images["imagenGrande"].src = rutaImagen;
		switch(so)
		{
			case 'ie' :
				document.images["imagenGrande"].filters.alpha.opacity = 0;
				break;

			case 'w3c' :
				document.images["imagenGrande"].style.opacity = 0;
				break;

			case 'moz' :
				document.images["imagenGrande"].style.MozOpacity = 0;
				break;

			default:
				break;
		}
    	degradado();
}

function quitarImagen( ){
    	cambiarTituloImagen("");

		degradadoFinalizar();
		switch(so)
		{
			case 'ie' :
				document.images["imagenGrande"].filters.alpha.opacity = 99;
				break;

			case 'w3c' :
				document.images["imagenGrande"].style.opacity = 0.99;
				break;

			case 'moz' :
				document.images["imagenGrande"].style.MozOpacity = 0.99;
				break;

			default:
				cambiarImagen("../images/gris.jpg", "");
				break;
		}
    	degradadoInverso();

    	cambiarImagen("../images/gris.jpg", "");
}

function cambiarTituloImagen( titulo ) {
	var tituloImagen = document.getElementById("tituloImagen");
	tituloImagen.innerHTML = titulo;
}