Little Boxes

Next we can start at the left hand end of each line (of the original image, not the dilated one!) and locate the first black pixel. This may be the bottom half of a character of text in the line above, the page number of the page, some noise from the book spine via an out of focus scanner, or a bit of a thumb-print or soup stain or worse. Since we have estimates of the character height obtained from the thickening, we can make an estimate of where the bottom of the character should be if we actually have the top left hand pixel of a character, and also have some ideas about where the rest of it should be. These will be very crude, because we might have an /o/, or a /b/ or a /p/ or a /q/, not to mention capitals or punctuation. If we have confidence in our knowledge of the font, we can look for vertical (relative to the direction of the line as horizontal) and horizontal separating lines between which our character may be found.

It is common practice in the case of the Roman alphabet to fit slightly slanted lines from South-South-West to North-North East because, as a careful examination of the italic text shows, there is not in general a vertical separating line between well spaced characters in italic fonts. This can also happen with well spaced non-italic fonts as when TEX places the characters in a word such as

WAVE

and it should be noted that there may be no line slanted like: `/' separating characters, either.

It should be plain that separating out characters from each other and putting boxes around them is not usually the simple procedure one might have hoped for.