Alignment of Curved Text Strings for Enhanced OCR Readability
Thotreingam Kasar, Laboratoire Litis, A. G. Ramakrishnan · 2013
Conventional optical character recognition systems, designed to recognize linearly aligned text, perform poorly on document images that contain multi-oriented text lines. This paper describes a novel technique that can extract text lines of arbitrary curvature and align them horizontally. By invoking the spatial regularity properties of text, adjacent components are grouped together to obtain the text lines present in the image. To align each identified text line, we fit a B-spline curve to the centroids of the constituent characters and normal vectors are computed all along the resulting curve. Each character is then individually rotated such that the corresponding normal vector is aligned with the vertical axis. The method has been tested on images that contain text laid out in various forms namely arc, wave, triangular and combination of these with linearly skewed text lines. It yields 97.3% recognition accuracy on text strings where state-of-the-art OCRs fail before alignment.