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.device.extension/src/org/eclipse/birt/chart/device/swing/SwingRendererImpl.java
bo.getTop( ),
				bo.getWidth( ),
				bo.getHeight( ) );
		if ( flBackground instanceof ColorDefinition )
		{
			final ColorDefinition cd = (ColorDefinition) flBackground;
			_g2d.setColor( (Color) _ids.getColor( cd ) );
			_g2d.fill( r2d );
		}
		else if ( flBackground instanceof Gradient )
		{
			final Gradient g = (Gradient) flBackground;
			final ColorDefinition cdStart = (ColorDefinition) g.getStartColor( );
			final ColorDefinition cdEnd = (ColorDefinition) g.getEndColor( );
			
			double dAngleInDegrees = g.getDirection( );
			final double dAngleInRadians = ( ( -dAngleInDegrees * Math.PI ) / 180.0 );
			
			/*
			 * if (bCyclic) { }
			 */
			if ( dAngleInDegrees < -90 || dAngleInDegrees > 90 )
			{
				throw new ChartException( ChartDeviceExtensionPlugin.ID,
						ChartException.RENDERING,
						"exception.gradient.angle",
						new Object[]{
							new Double( dAngleInDegrees )
						},
						ResourceBundle.getBundle( Messages.DEVICE_EXTENSION,