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/AttributeSwitch.java
{
		if ( theEClass.eContainer( ) == modelPackage )
		{
			return doSwitch( theEClass.getClassifierID( ), theEObject );
		}
		else
		{
			List eSuperTypes = theEClass.getESuperTypes( );
			return eSuperTypes.isEmpty( ) ? defaultCase( theEObject )
					: doSwitch( (EClass) eSuperTypes.get( 0 ), theEObject );
		}
	}
	/**
	 * Calls <code>caseXXX</code> for each class of the model until one returns a non null result; it yields that result.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @return the first non-null result returned by a <code>caseXXX</code> call.
	 * @generated
	 */
	protected Object doSwitch( int classifierID, EObject theEObject )
	{
		switch ( classifierID )
		{
			case AttributePackage.ACTION_VALUE :
			{
				ActionValue actionValue = (ActionValue) theEObject;
				Object result = caseActionValue( actionValue );
				if ( result == null )
					result = defaultCase( theEObject );
				return result;