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
* @see #getNumberFormatSpecifier()
	 * @generated
	 */
	EAttribute getNumberFormatSpecifier_FractionDigits( );
	/**
	 * Returns the meta object for class '{@link org.eclipse.birt.chart.model.attribute.Palette <em>Palette</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for class '<em>Palette</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.Palette
	 * @generated
	 */
	EClass getPalette( );
	/**
	 * Returns the meta object for the attribute '{@link org.eclipse.birt.chart.model.attribute.Palette#getName <em>Name</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for the attribute '<em>Name</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.Palette#getName()
	 * @see #getPalette()
	 * @generated
	 */
	EAttribute getPalette_Name( );
	/**
	 * Returns the meta object for the containment reference list '{@link org.eclipse.birt.chart.model.attribute.Palette#getEntries <em>Entries</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for the containment reference list '<em>Entries</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.Palette#getEntries()
	 * @see #getPalette()
	 * @generated
	 */
	EReference getPalette_Entries( );