Detecting the skew angle in document images

Abstract

In the field of document image analysis, accurate detection and removal of intrinsic skew is of paramount importance as a first step in the processing of document images. Here we present an efficient scheme for detecting the degree of misalignment in a document page. The proposed algorithm operates directly on the raw digitised image and is shown to achieve a high skew detection accuracy for mixed mode document formats which contain typewritten text, cursive script, line-art and photographic pictures. We also discuss efficiency considerations for a practical real-time hardware implementation of the algorithm. Furthermore, in a practical document image processing environment, it is necessary to process documents that are landscape or portrait oriented. In this context we present an algorithm which determines the page orientation prior to skew detection.