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.ui.extension/src/org/eclipse/birt/chart/ui/swt/composites/IconCanvas.java
/**
	 * Adjust the image onto the canvas
	 */
	public void fitCanvas( )
	{
		if ( sourceImage == null )
			return;
		Rectangle imageBound = sourceImage.getBounds( );
		Rectangle destRect = getClientArea( );
		double sx = (double) destRect.width / (double) imageBound.width;
		double sy = (double) destRect.height / (double) imageBound.height;
		double s = Math.min( sx, sy );
		double dx = 0.5 * destRect.width;
		double dy = 0.5 * destRect.height;
		centerZoom( dx, dy, s, new AffineTransform( ) );
	}
	/**
	 * Show the image with the original size
	 */
	public void showOriginal( )
	{
		if ( sourceImage == null )
			return;
		transform = new AffineTransform( );
		syncScrollBars( );
	}
	
	/**
	 * Clear the canvas
	 */