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/AttributeFactory.java
/**
	 * Returns a new object of class '<em>Text Alignment</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Text Alignment</em>'.
	 * @generated
	 */
	TextAlignment createTextAlignment( );
	/**
	 * Returns a new object of class '<em>Tooltip Value</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Tooltip Value</em>'.
	 * @generated
	 */
	TooltipValue createTooltipValue( );
	/**
	 * Returns a new object of class '<em>URL Value</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>URL Value</em>'.
	 * @generated
	 */
	URLValue createURLValue( );
	/**
	 * Returns the package supported by this factory.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the package supported by this factory.
	 * @generated
	 */
	AttributePackage getAttributePackage( );
}