RMS coordinate discrepancy as accuracy criterion of images normalization at optical document recognition
Optical text recognition on an image made from an arbitrary angle requires preliminary normalization of the image - transformation to such a view as if it had been obtained from a convenient angle for recognition. In this case, inaccuracies in normalization lead to recognition errors. To date, a number of accuracy criteria of normalization have been proposed in the literature, but their compliance with the quality of recognition is not studied. In this paper, for the case of a document with a fixed structure, a normal probabilistic recognition model is introduced, according to which the probability of correct recognition of a character decreases along the Gaussian with an increase in the discrepancy of the coordinates of this character. For this model, it was proved that the the accuracy criterion of image normalization, which is equal to RMS (root mean square) coordinate discrepancy over the text fields of the document, is monotonically related to the probability of the correct recognition of the entire document. Finally, RMS coordinate discrepancy for important case of projective normalization and region of interest consisting of rectangles was calculated analytically for the first time.