Some Useful Definitions

This section defines some terms and concepts used in this chapter.

affine rectangle: A quadrilateral where the opposite sides are parallel to each other

mark rectangle: A rectangle that specifies the x and y extents of a character in the rectified image.

cell rectangle: A rectangle that is in the same image coordinates as the rectified image and that provides information about the mark rectangle's position with respect to the read line. The cell rectangle can be used for discriminating characters with different sizes/positions (such as capital O versus lower-case o) based on character sizes with respect to other character sizes in the string.

See the following figure for mark rectangles and cell rectangles.

pitch: The distance between (approximately) corresponding points on adjacent characters.

Note: It is not the distance from the end of one character to the beginning of the next character (which is called the inter-character gap).

rotation: The turning of an object or rectangle about an axis point or center.

skew: The distortion of a rectangle into a parallelogram.