Hough technique for bar charts detection and recognition in document images

Charts are common graphic representation for scientific data in technical and business papers. We present a robust system for detecting and recognizing bar charts. The system includes three stages, preprocessing, detection and recognition. The kernel algorithm in detection is newly developed modified probabilistic Hough transform algorithm for parallel lines clusters detection. The main algorithms in recognition are bar pattern reconstruction and text primitives grouping in the Hough space which are also original. The experiments show the system can also recognize slant bar charts, or even hand-drawn charts.