Bug 190981 The image id of image in different pages are the same
The id of image generated by the same report item (such as chart) are the same, thought the image contents are in different pages.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/Image.java
* image source
	 */
	protected int source = IImage.INVALID_IMAGE;
	/**
	 * Comment for <code>data</code>
	 */
	protected byte[] data = null;
	
	protected String mimeType;
	
	protected String imageMap;
	/**
	 * Constructor with an image uri
	 * 
	 * @param uri
	 */
	public Image( String uri )
	{
		if ( uri == null || uri.length( ) == 0 )
		{
			return;
		}
		id = uri;
		if ( !FileUtil.isLocalResource( uri ) )
		{
			extension = FileUtil.getExtFromFileName( uri );
			this.source = IImage.URL_IMAGE;
			return;
		}
		this.source = IImage.FILE_IMAGE;