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
/**
	 * The meta object id for the '<em>Rule Type Object</em>' data type.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.RuleType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getRuleTypeObject()
	 * @generated
	 */
	int RULE_TYPE_OBJECT = 97;
	/**
	 * The meta object id for the '<em>Scale Unit Type Object</em>' data type.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.ScaleUnitType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getScaleUnitTypeObject()
	 * @generated
	 */
	int SCALE_UNIT_TYPE_OBJECT = 98;
	/**
	 * The meta object id for the '<em>Sort Option Object</em>' data type.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.SortOption
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getSortOptionObject()
	 * @generated
	 */
	int SORT_OPTION_OBJECT = 99;
	/**
	 * The meta object id for the '<em>Stretch Object</em>' data type. <!--
	 * begin-user-doc --> <!-- end-user-doc -->
	 * 
	 * @see org.eclipse.birt.chart.model.attribute.Stretch
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getStretchObject()