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/AttributePackage.java
/**
	 * Returns the meta object for data type '{@link org.eclipse.birt.chart.model.attribute.UnitsOfMeasurement <em>Units Of Measurement Object</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for data type '<em>Units Of Measurement Object</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.UnitsOfMeasurement
	 * @model instanceClass="org.eclipse.birt.chart.model.attribute.UnitsOfMeasurement"
	 *        extendedMetaData="name='UnitsOfMeasurement:Object' baseType='UnitsOfMeasurement'" 
	 * @generated
	 */
	EDataType getUnitsOfMeasurementObject( );
	/**
	 * Returns the meta object for data type '{@link org.eclipse.birt.chart.model.attribute.VerticalAlignment <em>Vertical Alignment Object</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for data type '<em>Vertical Alignment Object</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.VerticalAlignment
	 * @model instanceClass="org.eclipse.birt.chart.model.attribute.VerticalAlignment"
	 *        extendedMetaData="name='VerticalAlignment:Object' baseType='VerticalAlignment'" 
	 * @generated
	 */
	EDataType getVerticalAlignmentObject( );
	/**
	 * Returns the factory that creates the instances of the model. <!--
	 * begin-user-doc --> <!-- end-user-doc -->
	 * 
	 * @return the factory that creates the instances of the model.
	 * @generated
	 */
	AttributeFactory getAttributeFactory( );
}