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 -->
	 * @return the meta object for the containment reference list '<em>Angles</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.Rotation3D#getAngles()
	 * @see #getRotation3D()
	 * @generated
	 */
	EReference getRotation3D_Angles( );
	/**
	 * Returns the meta object for class '{@link org.eclipse.birt.chart.model.attribute.ScriptValue <em>Script Value</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for class '<em>Script Value</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.ScriptValue
	 * @generated
	 */
	EClass getScriptValue( );
	/**
	 * Returns the meta object for the attribute '{@link org.eclipse.birt.chart.model.attribute.ScriptValue#getScript <em>Script</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for the attribute '<em>Script</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.ScriptValue#getScript()
	 * @see #getScriptValue()
	 * @generated
	 */
	EAttribute getScriptValue_Script( );
	/**
	 * Returns the meta object for class '{@link org.eclipse.birt.chart.model.attribute.SeriesValue <em>Series Value</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for class '<em>Series Value</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.SeriesValue