Bug 104986 Backgound image uses an absolute path
Currently Chart uses an absolute path to indicate a backgournd image, that may cause the design unusable on other environments. Expected the background image can be definded in multiple ways like in report designer. e.g. URI(absolute path), File(relative path), Embedded Image(Encoded Image Data).
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/model/attribute/impl/AttributeFactoryImpl.java
return createSeriesValue( );
			case AttributePackage.SIZE :
				return createSize( );
			case AttributePackage.STYLE :
				return createStyle( );
			case AttributePackage.STYLE_MAP :
				return createStyleMap( );
			case AttributePackage.TEXT :
				return createText( );
			case AttributePackage.TEXT_ALIGNMENT :
				return createTextAlignment( );
			case AttributePackage.TOOLTIP_VALUE :
				return createTooltipValue( );
			case AttributePackage.URL_VALUE :
				return createURLValue( );
			default :
				throw new IllegalArgumentException( "The class '" + eClass.getName( ) + "' is not a valid classifier" ); 
		}
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public Object createFromString( EDataType eDataType, String initialValue )
	{
		switch ( eDataType.getClassifierID( ) )
		{
			case AttributePackage.ACTION_TYPE :
			{
				ActionType result = ActionType.get( initialValue );