Method for data compression for two-value picture image

• US 4,566,128 A
• Filed: 07/18/1983
• Issued: 01/21/1986
• Est. Priority Date: 09/13/1982
• Status: Expired due to Fees

• Current Assignee: Dainippon Screen Graphics (USA) LLC (SCREEN Holdings Co., Ltd.)
• Original Assignee: Dainippon Screen Graphics (USA) LLC (SCREEN Holdings Co., Ltd.)
• Inventors: Araki, Shuichi
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US06/514,674
• Time in Patent Office: 918 Days
• Field of Search: 358/133, 358/138, 358/260, 358/261, 358/263, 382/22, 382/56, 382/54, 382/60, 364/518, 340/750, 340/798-801
• US Class Current: 382/242
• CPC Class Codes: B41B 19/01 having electron-beam tubes producing an image of at least one character which is photographed
• CPC Class Codes: G06F 3/002 Specific input/output arrangements not covered by G06F3/01 - G06F3/16 other optical apparatus G02B27/00
• CPC Class Codes: G06F 3/018 Input/output arrangements for oriental characters
• CPC Class Codes: G09G 5/246 of ideographic or arabic-like characters

Abstract

A method for compressing the data of character images primarily for a font set for kanji (Chinese character) photo-type-setting characterized by the steps of dividing up an original picture image into a plurality of partial picture images, identifying the contour lines in each of the partial picture images by finding a start point and an end point for each of the contour line segments as well as those points which characterize the configuration of each contour line segment, connecting the start points with the corresponding end points so as to determine a group of closed-loop line segments as an aggregate of the contour lines and to represent the original picture image, and storing the date of this original picture in the form of a group of closed-loop line segments in a memory in a highly compressed form through elimination of coordinate point data which may be identified by less redundant information.

Claims

1. Method for data compression for two-value picture image, characterized by the steps of:

dividing an original picture image into a plurality of partial picture images;

determining a start point and an end point of each contour line found in each of the partial picture images by finding the intersections between the contour line and the lines dividing the original picture image into the partial picture images;

detecting characteristic points in each contour line by tracing the contour line in each of the partial picture images from the corresponding start point and end point;

extracting those start points and end points which connect to those in the neighboring partial picture images and the characteristic points as necessary coordinate points for determining a group of closed-loop line segments as an aggregate of the contour lines; and

further compressing the data of the original picture image by removing any redundant coordinate point data through comparison of the gradients of the closed-loop line segments for each neighboring coordinate point pairs on the particular contour line.

2. Method as defined in claim 1, wherein each characteristic point of the contour lines is selected on the basis of the directions of two vectors of the coordinate points adjacent to the particular coordinate point of interest along the particular contour line, the coordinate points corresponding to the locations of the pixel bits along the contour line.

3. Method as defined in claim 2, wherein the redundant coordinate point data is comprised of those coordinate points which have the same gradients to the preceding coordinate points along the contour lines.