Real time binarization of gray images
AssigneeLockheed Martin Corporation
InventorRichard C. Van Hall
Life of this patent
Estimating the term…
Abstract
A binarization method for gray address images which combines high quality and high speed. The method is designed specifically for efficient software implementation. Two binarization approaches, localized background thresholds and Laplacian edge enhancement, are combined into a process to enhance the strengths of the two methods and eliminate their weaknesses. The image is divided into tiles, making binarization decisions for each tile. Tile decisions are modified based on adjacent tile decisions and then the tiles are binarized. Binarization of pixels is performed by performing background thresholding and edge detection thresholding. Only pixels exceeding both thresholds are selected as “on”.
Claims12
A computer implemented method for real time binarization of gray scale images, said method comprising the steps of:
- receiving an initial gray scale image;
- dividing the initial gray scale image into a plurality of tiles;
- determining for each tile in the plurality of tiles whether it is to be categorized as a background tile or a binarization tile, based on a sub-sampling of pixels in the tile;
- saving the categorization information for the each tile in the plurality of tiles;
- updating the saved categorization information for each tile by examining binarization flags for neighboring tiles to determine whether the number of neighboring tiles flagged for binarization is above a desired threshold, and if so, then setting the binarization flag “on” for the tile, but if not, then setting the binarization flag “off” for the tile;
- binarizing the plurality of tiles, including steps of background thresholding and edge detection, in accordance with said binarization flags by combining results of background thresholding and results of edge detection, thereby creating a binarized image readable by an optical character recognition means.
A system for sorting mail comprising:
- means for imaging a piece of mail, the means generating a machine readable gray image;
- a computing device for generating a binarized image of the machine readable gray image, wherein the machine readable gray image is divided into a plurality of tiles, each tile in the plurality of tiles is categorized as a background tile or a binarization tile based on a sub-sampling of pixels within each tile to provide binarization information, the resulting categorization information for each tile in the plurality of tiles being saved, each tile determined as being selected for a categorization information update, or not, based on neighboring tile categorization, the categorization information for each tile in the plurality of tiles being updated as necessary in accordance with the number of neighboring tiles having different categorization information;
- selectively performing binarization of respective tiles in accordance with said categorization information, as updated;
- and
- sorting the piece of mail based on selected criteria relating to the binarized image generated by the computing device.
Dependencies are inferred from the claim text.