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
{
	/**
	 * The cached model package
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @generated
	 */
	public static final AttributeValidator INSTANCE = new AttributeValidator( );
	/**
	 * A constant for the {@link org.eclipse.emf.common.util.Diagnostic#getSource() source} of diagnostic {@link org.eclipse.emf.common.util.Diagnostic#getCode() codes} from this package.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.emf.common.util.Diagnostic#getSource()
	 * @see org.eclipse.emf.common.util.Diagnostic#getCode()
	 * @generated
	 */
	public static final String DIAGNOSTIC_SOURCE = "org.eclipse.birt.chart.model.attribute"; 
	/**
	 * A constant with a fixed name that can be used as the base value for additional hand written constants.
	 * <!-- begin-user-doc --> <!--
	 * end-user-doc -->
	 * @generated
	 */
	private static final int GENERATED_DIAGNOSTIC_CODE_COUNT = 0;
	/**
	 * A constant with a fixed name that can be used as the base value for additional hand written constants in a derived class.
	 * <!-- begin-user-doc
	 * --> <!-- end-user-doc -->
	 * @generated
	 */