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/presentation/LocalizedContentVisitor.java
case IReportItemPresentation.OUTPUT_AS_CUSTOM :
				IDataContent dataObj = reportContent.createDataContent( content );
				dataObj.setValue( output );
				processData( dataObj );
				return dataObj;
			case IReportItemPresentation.OUTPUT_AS_HTML_TEXT :
				content.setRawType( IForeignContent.HTML_TYPE );
				content.setRawValue( output.toString( ) );
				return content;
			case IReportItemPresentation.OUTPUT_AS_TEXT :
				ITextContent textObj = reportContent.createTextContent( );
				textObj.setText( output.toString( ) );
				return textObj;
				
			default :
				assert false;
				logger.log( Level.WARNING, "unsupported output format:{0}", 
						new Integer( type ) );
		}
		return content;
	}
	/**
	 * read the content of input stream.
	 * 
	 * @param in
	 *            input content
	 * @return content in the stream.
	 */
	static protected byte[] readContent( InputStream in )
	{