Bug 195335 Multithreads issue
a static hashmap in class HTMLServerImageHandler has not been synchronized which may leads to that the same images are handled(eg: write to disk) multiple times.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/HTMLServerImageHandler.java
/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.engine.api2.IHTMLImageHandler#onDocImage(org.eclipse.birt.report.engine.api2.IImage,
	 *      java.lang.Object)
	 */
	public String onDocImage( IImage image, Object context )
	{
		
		return null;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.engine.api2.IHTMLImageHandler#onURLImage(org.eclipse.birt.report.engine.api2.IImage,
	 *      java.lang.Object)
	 */
	public String onURLImage( IImage image, Object context )
	{
		assert ( image != null );
		String uri = image.getID( );
		if (uri.startsWith( "http:" ) || uri.startsWith( "https:" ))
		{
			return uri;
		}
		return handleImage( image, context, "uri", true ); 
	}
	/*
	 * (non-Javadoc)
	 *