1. An optical-symbol-recognition system comprising: one or more processors; one or more memories; one of more data-storage devices; and computer instructions, stored in one or more of the one or more data-storage devices that, when executed by one or more of the one or more processors, control the optical-symbol-recognition system to process a text-containing scanned image of a document by: identifying symbol images in the text-containing scanned image of the document; for each page in the document, for each symbol image in the page, identifying each grapheme of a set of graphemes that matches the normalized symbol image with respect to a symbol pattern is a set of symbol patterns, sorting the identified graphemes according to a frequency with which the identified graphemes match the normalized symbol image with respect to symbol patterns in the set of symbol patterns, and using the sorted identified graphemes to select a symbol code that represents the normalized symbol image; and preparing a processed document containing symbol codes that represent the normalized symbol images in the scanned image of the document and storing the processed document in one or more of the one of more data-storage devices and memories.