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>Data Point Component Type Object</em>' data type.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.DataPointComponentType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getDataPointComponentTypeObject()
	 * @generated
	 */
	int DATA_POINT_COMPONENT_TYPE_OBJECT = 75;
	/**
	 * The meta object id for the '<em>Data Type Object</em>' data type.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.DataType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getDataTypeObject()
	 * @generated
	 */
	int DATA_TYPE_OBJECT = 76;
	/**
	 * The meta object id for the '<em>Date Format Detail Object</em>' data type.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.DateFormatDetail
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getDateFormatDetailObject()
	 * @generated
	 */
	int DATE_FORMAT_DETAIL_OBJECT = 77;
	/**
	 * The meta object id for the '<em>Date Format Type Object</em>' data type.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.DateFormatType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getDateFormatTypeObject()
	 * @generated