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
* <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.AngleType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getAngleType()
	 * @generated
	 */
	int ANGLE_TYPE = 38;
	/**
	 * The meta object id for the '{@link org.eclipse.birt.chart.model.attribute.ChartType <em>Chart Type</em>}' enum.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.ChartType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getChartType()
	 * @generated
	 */
	int CHART_TYPE = 41;
	/**
	 * The meta object id for the '{@link org.eclipse.birt.chart.model.attribute.DataPointComponentType <em>Data Point Component Type</em>}' enum.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.DataPointComponentType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getDataPointComponentType()
	 * @generated
	 */
	int DATA_POINT_COMPONENT_TYPE = 42;
	/**
	 * The meta object id for the '{@link org.eclipse.birt.chart.model.attribute.DataType <em>Data Type</em>}' enum.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.DataType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getDataType()
	 * @generated
	 */