CHARACTER VIDEO ENHANCEMENT SYSTEM

• US 3,737,855 A
• Filed: 09/30/1971
• Issued: 06/05/1973
• Est. Priority Date: 09/30/1971
• Status: Expired due to Term

• Current Assignee: Alfred Cutaia
• Original Assignee: Alfred Cutaia
• Inventors: Cutaia, Alfred
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Boudreau, Leo H.
• Application Number:
  US05/185,214
• Time in Patent Office: 614 Days
• Field of Search: 340/146.3H,146.3AG,146.3MA
• US Class Current: 382/272
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/20 Combination of acquisition, preprocessing or recognition functions

Abstract

Disclosed herein is a character video enhancement system which functions to minimize undesirable black fillins, noise and white voids in character patterns. The characters and noise patterns may be viewed as comprised of pluralities of elemental areas. Enhancement is accomplished by using a series of algorithms which enables a decision to be made at each elemental area as to whether a black mark in an elemental area should be converted to a white mark, or a white mark to a black mark or left black or white. The decision made at each elemental area is made independent of the raw video at that area and depends only on the markings in neighboring areas. For each elemental area, the surrounding neighborhood is investigated to determine: A. THE PROBABILITY E that the surrounding elemental areas are not part of an a priori defined primitive feature set given that the elemental area under consideration is assumed to contain a white mark; B. THE PROBABILITY I that the surrounding elemental areas are part of the a priori defined primitive feature set given that the elemental area under consideration is assumed to contain a black mark; and C. THRESHOLD LEVELS TE and TI determined on the basis of contrast measurements. The probabilities E AND I are compared with the threshold levels TE and TI to determine whether the content of the elemental area under consideration should be altered or left as is.

Claims

1. In a character recognition system, a process for modifying raw character video obtained from a document to cause the character features to approach a predefined primitive feature set, the process comprising the steps of:

a. scanning the document over a plurality of elemental areas thereof, and detecting the presence or absence of a marking in each scanned elemental area, b. generating for each scanned elemental area a black or white bit corresponding respectively to the presence or absence of a predetermined quantity of marking in the area, c. determining, in response to the black and white bits generated by the elemental areas surrounding an elemental area under consideration, a probability I that the surrounding areas are part of the primitive feature set assuming that the bit corresponding to the area under consideration is a black bit, d. determining, in response to the black and white bits generated by the elemental areas surrounding the element area under consideration, a probability E that the surrounding areas are not part of the primitive feature set assuming that the bit corresponding to the area under consideration is a white bit, e. generating contrast measurements indicative of the relative numbers of black and white bits generated by selected groups of the plurality of elemental areas, f. determining from the contrast measurements threshold levels TE and TI and g. comparing the probabilities I and E with the threshold levels TE and TI to selectively complement the bit generated by the area under consideration.

2. The process of claim 1 further including, a. storing generated bits in a matrix type serial shift register, each new bit entering the register causing previously stored bits to shift through succeeding register stages, b. designating a mask area within said shift register, c. designating a decision bit location XKJ within said mask area, each bit entering said register passing through said XKJ location as a result of additional bits entering the register, d. determining the probabilities I and E from a determination of the states of the shift register stages surrounding the XKJ location.

3. The process of claim 2 wherein said step of determining the probabilities I and E further include;

a. detecting if the generated bit at the XKJ location represents an elemental area situated at the boundary of a pattern feature of which the bit at the XKJ location is a part. b. defining a criteria set for determinating if the bit at the XKJ location is part of a primitive feature within the primitive feature set, assuming the bit at the XKJ location is a black bit, and c. for each bit determined to be a boundary bit calculating on the basis of the defined criteria set, the probabilities I and E.

4. The process of claim 3 wherein said probabilities are proportional to I (BD1) Smax maj + BD1, where BD1 indicates that the XKJ location represents an elemental area situated at a boundary of a pattern feature, and Smax maj indicates the maximum extent to which a predetermined group of said elemental areas matches any predetermined feature within said primitive feature set, and E 1-I.

5. The process of claim 4 wherein said step of defining a mask area comprises, selecting a maximum desired stroke width, and setting thE mask area to be large enough to completely contain the two boundaries of a feature with a maximum stroke width with one boundary being position at the XKJ position.

6. The process of claim 5 wherein said step of defining a primitive feature comprises defining four primitive features consisting of a horizontal line, a vertical line, and a first and second diagonal line positioned respectively at a positive 45* slope and a negative 45* slope, each of said primitive features having said maximum desired stroke width.

7. The process of claim 6 wherein said step of boundary determination comprises investigating the first level register stages surrounding the XKJ location to determine the presence of a white bit.

8. The process of claim 2 wherein the step of calculating the threshold levels TE and TI comprise the steps of;

a. calculating the local contrast BKJ about the location XKJ, b. calculating the average limited area sum SKJ over the adjacent preceeding scan, c. calculating the average character area contrast AKJ over N preceeding scans and d. combining said calculated values to determine TE and TI.

9. The process of claim 8 wherein said step of combining includes;

a. determining the maximum permissible value of BKJ on the basis of an a priori selected stroke width, b. determining if the character area contrast AKJ is greater than the maximum permissible BKJ, c. selecting a low constant value for TE and a high constant value for TI if AKJ is greater than the maximum permissible value for BKJ,

10. A character enhancement system comprising:

a. means for scanning a document in a series of elemental scans, each elemental scan viewing an elemental area of said document, b. means for detecting the presence or absence of a marking in each scanned elemental area, said detecting means producing electrical signals representing black and white bits corresponding respectively to the presence and absence of a marking in each elemental area, c. register means for storing said black and white bits, and d. means for selectively generating the complement of each stored bit, said means including means adapted to calculate for each bit entered into said register a probability I that the elemental areas surrounding the elemental area represented by said each bit is part of a defined primitive feature set, assuming said each bit is a black bit, calculate for each bit entered into said register a probability E that the elemental areas surrounding the elemental area represented by said each bit is not part of the primitive feature set, assuming said each bit is a white bit, calculate contrast indicia representing the contrast about said each bit, determine, on the basis of the calculated contrast indicia contrast threshold levels TE and TI and compare the probabilities I and E with the threshold levels TE and TI.

11. The character enhancement system of claim 10 wherein said register means is a shift register including a mask area and a decision bit location XKJ within said mask area, said means for selectively generating operating on each bit as it is stored in said XKJ location.

12. The character enhancement system of claim 11 further including output register means for storing bits corresponding to the bits in said matrix type shift register means and having values determined by said means for selectively generating.

13. The character enhancement system of claim 11 wherein said means for selectively generating includes means for solving the algorithm I (BD1)Smax maj+BD1 and E 1 - I wherein BD1 defines the first order boundary about the decision bit location XKJ and Smax maj number of bits matching the primitive feature, of the primitive feature, set having the greatest majority of satisfied bits divided by the total number of bits which define the primitive feature.