function previous_image( normal_class, selected_class )
{
	if( slide_pointer < 3 )
	{
		document.getElementById( 'kep_lepteto_elozo' ).style.display = "none";
		document.getElementById( 'kep_lepteto_elozo_rejtett' ).style.display = "";
	}
	if( slide_pointer == 1 )
	{
		return false;
	}
	var disabled_column = slide_pointer + displayed_images - 1;
	var enabled_column = slide_pointer - 1;
	document.getElementById( column_prefix + disabled_column ).style.display = "none";
	document.getElementById( column_prefix + enabled_column ).style.display = "";
	document.getElementById( 'kep_lepteto_kovetkezo' ).style.display = "";
	document.getElementById( 'kep_lepteto_kovetkezo_rejtett' ).style.display = "none";
	slide_pointer--;
}

function next_image( normal_class, selected_class )
{
	if(  slide_pointer + displayed_images >= image_number )
	{
		document.getElementById( 'kep_lepteto_kovetkezo' ).style.display = "none";
		document.getElementById( 'kep_lepteto_kovetkezo_rejtett' ).style.display = "";
	}
	if( slide_pointer + displayed_images > image_number )
	{
		return false;
	}
	var disabled_column = slide_pointer;
	var enabled_column = slide_pointer + displayed_images;
	document.getElementById( column_prefix + disabled_column ).style.display = "none";
	document.getElementById( column_prefix + enabled_column ).style.display = "";
	document.getElementById( 'kep_lepteto_elozo' ).style.display = "";
	document.getElementById( 'kep_lepteto_elozo_rejtett' ).style.display = "none";
	slide_pointer++;
}