Method for establishing pixel colour probabilities for use in ocr logic

A method of creating a decision tree to enable a character recognition device to recognise characters in a new unknown font includes scanning a document printed in the unknown font to generate an array of pixels, with each pixel having a neighbourhood state based on the colours of the surrounding pixels. A plurality of clusters of pixels, each representing a printed character, are identified. A pixel in one cluster is selected, and its neighbourhood state determined. The neighbourhood state is used to address a memory that has stored in it a probability table providing the probability, in a second font different from the new font being taught, that a pixel is black as a function of its neighbourhood state. The stored probability of black associated with the neighbourhood state of the select pixel is read from the memory and assigned as the probability of the selected pixel. The decision tree for the new font is generated using that assigned probability of black.