20. The computing system of claim 17 , wherein the images correspond to pages within a book, and the image of the text corresponds to one of an odd-numbered page within the book and an even-numbered page within the book, wherein where the image corresponds to an odd-numbered page within the book, the logic is to determine the valid content boundary based on the images that correspond to odd-numbered pages within the book, and wherein where the image corresponds to an even-numbered page within the book, the logic is to determine the valid content boundary based on the images that correspond to even-numbered pages within the book.
17. A computing system comprising: a processor; a computer-readable data storage medium to store first data representing an image of text and a marking other than the text, and second data representing the text and the marking in non-image form, the marking represented within the second data as if the marking were part of the text; and logic executable by the processor to determine a valid content boundary within the image, the valid content boundary dividing a portion of the image corresponding to the text from and excluding another portion of the image corresponding to the marking, and for each character of a plurality of characters within the second data, to remove the character from the second data where the logic has determined that a location of an image portion within the first data corresponding to the character falls outside the valid content boundary.