Patent GB-1472443-A (GB)
Title: Method of and apparatus for recognition of characters
IPC: G06V30/10
Filed: 1974-07-30
Abstract: 1472443 Character recognition systems DE STAAT DER NEDERLANDEN REPRESENTED BY DE DIRECTEUR GENERAAL DER POSTERIJEN TELEGRAFIE EN TELEFONIE 30 July 1974 [30 July 1973 15 March 1974 19 April 1974] 33611/74 Heading G4R During a training mode features are derived from a number of hand-written representations of a reference character. The number of occurrences of a particular feature in the representations is determined to provide a logarithmic probability value indicating the likelihood of that feature being present in that character. Logarithmic probability values are obtained similarly for other features relating to that character. Values are also obtained in respect of each other character of a set of reference characters. In the recognition mode the logarithmic probability values corresponding to the features found in the unknown character are summed in respect of each of the reference characters, the largest sum identifying the reference character most similar to the unknown. The system involves the inspection of an electrical image of a handwritten character from a number of different directions, situated both within and without the character field, in order to derive characteristic features. For example, the character may be viewed from the outside of the character looking down, up, right, and left, Fig. 2a-2d. It may also be viewed from a centre line and looking right, left, up and down, Figs. 2e-2h. Those character portions which are seen unshadowed by other portions (shown in full line in Fig. 2a-2h) are those used to determine the features for each direction. The scanned image is binarized and passed to a matrix store. Signals are read from the store and processed. By suitably addressing the store the read-out may effectively represent the image in any of four orientations, corresponding to the directions of view mentioned above, and may also be displaced vertically or horizontally, effectively providing views from the centre line. The image is centred in the matrix by reference to the positions of the horizontal and vertical projections of it. The various features of the image which are determined for each of the directions of view as follows: (a) The position of the beginning of one character portion relative to that of the beginning of the next portion is determined as + or -. For example, if the image is viewed as in Fig. 2c and the store is read out row by row starting from the top the beginning of the first or topmost portion (the peak of the 2) is found to lie nearer the viewer than the beginning of the next portion; this may be regarded as a- . For each view direction a value is recorded indicating the succession of relative positions. For example for Fig. 2c the succession indicated is (b) The successive directions of slope in a character portion are determined, e.g. as +, -, or 0 and recorded as a corresponding value (Fig. 8-11 and 52, not shown). (c) The number of "terminal" points in the image is determined, such a point being at that end of a character portion which is nearest to the viewer. (d) The image is also processed so as to extract those areas of the character field that are shadowed by one or another character portion from each of the four outside viewing directions, e.g. the areas 011-013 in Fig. 18. Areas such as 012, 013 separated by a sufficiently small region of background are regarded as a single area. For each direction a value is recorded indicative of the number of areas and whether they are bordered by a character portion or by background, when considered from that direction. For example, when viewed from the top the area 011 is bordered by background and area 012, 013 by a character portion.