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
int DATA_TYPE = 43;
	/**
	 * The meta object id for the '{@link org.eclipse.birt.chart.model.attribute.DateFormatDetail <em>Date Format Detail</em>}' enum.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.DateFormatDetail
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getDateFormatDetail()
	 * @generated
	 */
	int DATE_FORMAT_DETAIL = 44;
	/**
	 * The meta object id for the '{@link org.eclipse.birt.chart.model.attribute.DateFormatType <em>Date Format Type</em>}' enum.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.DateFormatType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getDateFormatType()
	 * @generated
	 */
	int DATE_FORMAT_TYPE = 45;
	/**
	 * The meta object id for the '{@link org.eclipse.birt.chart.model.attribute.Direction <em>Direction</em>}' enum.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.Direction
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getDirection()
	 * @generated
	 */
	int DIRECTION = 46;
	/**
	 * The meta object id for the '{@link org.eclipse.birt.chart.model.attribute.GroupingUnitType <em>Grouping Unit Type</em>}' enum.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @see org.eclipse.birt.chart.model.attribute.GroupingUnitType
	 * @see org.eclipse.birt.chart.model.attribute.impl.AttributePackageImpl#getGroupingUnitType()