Bug 140395 IImage.getID() return null on chart images
When I use image.getID() to retrieve ID of chart image, it always returns null.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/Image.java
*            the source stream
	 * @param tgt
	 *            the target stream
	 * @throws IOException
	 */
	protected void copyStream( InputStream src, OutputStream tgt )
			throws IOException
	{
		
		byte[] buffer = new byte[1024];
		int size = 0;
		do
		{
			size = src.read( buffer );
			if ( size > 0 )
			{
				tgt.write( buffer, 0, size );
			}
		} while ( size > 0 );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.engine.api.IImage#getExtension()
	 */
	public String getExtension( )
	{
		return extension;
	}
}