Detect the header and footer areas in a document, and set the appropriate properties of all the elements contained within those areas.
Sets the isHeader or isFooter property flags for each one of the elements detected as headers or footers respectively in the detected areas.
- It detects empty (or white) horizontal bands across the entire document (all pages), which do not contain an element.
- For the footer, the highest of these such bands, not exceeding the value L from the bottom is retained as the footer dividing line.
- For the header, the lowest of these bands is retained using the same algorithm, except that the distance is calculated form the top of the pages.
- The algorithm also detects page number mentions using regexp based matching inside the elements classified as headers or footers.
The following two parameters are available:
maxMarginPercentage: The percentage of the page up to which (both from the top and the bottom) the algorithm will search for header or footer classification.ignorePages: The list of pages to be ignored in the header/footer search. This typically includes book titles, table of contents, preface, and other pages which do not typically have the same header/footer layout as the rest of the document.similaritySizePercentage: The percentage represent the difference of size between pages. This allow to apply the maxMarginPercentage option within groups of pages of similar size.
Given a good maxMarginPercentage, very good.
The accuracy is directly proportional to the number of pages (samples) available to the algorithm.
- An omittance of non-useful pages (like the title page) in the
ignoredPageslist can produce a false negative.