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/util/AttributeSwitch.java
}
			case AttributePackage.DATE_FORMAT_SPECIFIER :
			{
				DateFormatSpecifier dateFormatSpecifier = (DateFormatSpecifier) theEObject;
				Object result = caseDateFormatSpecifier( dateFormatSpecifier );
				if ( result == null )
					result = caseFormatSpecifier( dateFormatSpecifier );
				if ( result == null )
					result = defaultCase( theEObject );
				return result;
			}
			case AttributePackage.EXTENDED_PROPERTY :
			{
				ExtendedProperty extendedProperty = (ExtendedProperty) theEObject;
				Object result = caseExtendedProperty( extendedProperty );
				if ( result == null )
					result = defaultCase( theEObject );
				return result;
			}
			case AttributePackage.FILL :
			{
				Fill fill = (Fill) theEObject;
				Object result = caseFill( fill );
				if ( result == null )
					result = defaultCase( theEObject );
				return result;
			}
			case AttributePackage.FONT_DEFINITION :
			{
				FontDefinition fontDefinition = (FontDefinition) theEObject;