I am learning OCR and reading this book The authors define 8 processes to implement OCR that follow one by one (2 after 1, 3 after 2 etc):Optical scanningLocation segmentationPre-processingSegmentationRepresentationFeature extractionRecognitionPost-processingThis is what they write about representation (#5)The fifth OCR component is representation. The image representation  plays one of the most important roles in any recognition system. In  the simplest case, gray level or binary images are fed to a  recognizer. However, in most of the recognition systems in order to  avoid extra complexity and to increase the accuracy of the algorithms,  a more compact and characteristic representation is required. For this  purpose, a set of features is extracted for each class that helps  distinguish it from other classes while remaining invariant to  characteristic differences within the class.The character image   representation methods are generally categorized into three major  groups: (a) global transformation and series expansion (b) statistical  representation and (c) geometrical and topological representation.This is what they write about feature extraction (#6)The sixth OCR component is feature extraction. The objective of  feature extraction is to capture essential characteristics of symbols.  Feature extraction is accepted as one of the most difficult problems  of pattern recognition. The most straight forward way of describing  character is by actual raster image. Another approach is to extract  certain features that characterize symbols but leaves the unimportant  attributes. The techniques for extraction of such features are divided  into three groups viz. (a) distribution of points (b) transformations  and series expansions and (c) structural analysis.I am totally confused. I don't understand what is representation. As I understand after segmentation we must take from image some features, for example topological structure like Freeman chain code and must match to some saved at the learning stage model - i.e. to do recognition. By other words - segmentation - feature extraction - recognition. I don't understand what must be done on representation stage. Please, explain.
What is representation in optical character recognition?
feature selection;feature extraction;feature engineering;ocr