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/util/AttributeValidator.java
public boolean validateLegendItemType( Object legendItemType,
			DiagnosticChain diagnostics, Map context )
	{
		return true;
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public boolean validateLineDecorator( Object lineDecorator,
			DiagnosticChain diagnostics, Map context )
	{
		return true;
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public boolean validateLineStyle( Object lineStyle,
			DiagnosticChain diagnostics, Map context )
	{
		return true;
	}
	/**
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public boolean validateMarkerType( Object markerType,
			DiagnosticChain diagnostics, Map context )
	{