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/impl/AttributeFactoryImpl.java
return createRuleTypeObjectFromString( eDataType, initialValue );
			case AttributePackage.SCALE_UNIT_TYPE_OBJECT :
				return createScaleUnitTypeObjectFromString( eDataType,
						initialValue );
			case AttributePackage.SORT_OPTION_OBJECT :
				return createSortOptionObjectFromString( eDataType,
						initialValue );
			case AttributePackage.STRETCH_OBJECT :
				return createStretchObjectFromString( eDataType, initialValue );
			case AttributePackage.STYLED_COMPONENT_OBJECT :
				return createStyledComponentObjectFromString( eDataType,
						initialValue );
			case AttributePackage.TICK_STYLE_OBJECT :
				return createTickStyleObjectFromString( eDataType, initialValue );
			case AttributePackage.TRIGGER_CONDITION_OBJECT :
				return createTriggerConditionObjectFromString( eDataType,
						initialValue );
			case AttributePackage.TRIGGER_FLOW_OBJECT :
				return createTriggerFlowObjectFromString( eDataType,
						initialValue );
			case AttributePackage.UNITS_OF_MEASUREMENT_OBJECT :
				return createUnitsOfMeasurementObjectFromString( eDataType,
						initialValue );
			case AttributePackage.VERTICAL_ALIGNMENT_OBJECT :
				return createVerticalAlignmentObjectFromString( eDataType,
						initialValue );
			default :
				throw new IllegalArgumentException( "The datatype '" + eDataType.getName( ) + "' is not a valid classifier" ); 
		}
	}