Method of storing characters in a display system

• US 4,633,243 A
• Filed: 03/23/1984
• Issued: 12/30/1986
• Est. Priority Date: 06/30/1983
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gay, Adrian C., Bowater, Ronald J., Bresenham, Jack E., Sheen, Norman R.
• Primary Examiner(s): Curtis, Marshall M.
• Assistant Examiner(s): Angotti, Donna
• Application Number:
  US06/592,675
• Time in Patent Office: 1,012 Days
• Field of Search: 340/732, 340/739, 340/740, 340/748, 340/731, 340/727, 340/741, 340/742, 315/365, 315/356
• US Class Current: 345/17
• CPC Class Codes: G09G 1/10 the deflection signals being produced by essentially digital means, e.g. incrementally
• CPC Class Codes: G09G 5/24 Generation of individual character patterns

Abstract

In a method of storing characters in a display system having a display device with an orthogonal matrix of addressable points, each character is represented as a succession of strokes each constrained to lie in one of the eight fundamental directions of the matrix and, except for the first stroke, each starting at the end of the previous stroke. Each such stroke is stored in a binary coded form which includes a first binary number (direction code) defining the angular direction of the stroke, a second binary number (length code) defining a number of matrix steps from one addressable point to the next along the stroke in that direction, and a third binary number (move/draw code) defining the visibility of the stroke. In order to facilitate character rotation by any multiple of 45° the direction code defining each fundamental direction corresponds to the addition modulo 2ⁿ of a binary constant to the direction code which defines the fundamental direction of 45° thereto in a given direction of rotation, where n is the number of bits in the direction code.

Claims

1. A method of storing characters in a display system having a display device with an orthogonal matrix of addressable points and drawing said stored characters on said display device, comprising the steps of:

representing each character as a succession of strokes each constrained to lie in one of eight fundamental directions of the matrix, and, except for a first stroke, each starting at an end of a previous stroke;

storing each such stroke in a binary coded form which includes a first binary number defining an angular direction of said stroke, a second binary number defining a number of matrix steps from one point to a next point along said stroke, and a third binary number defining a visibility characteristic of said stroke;

storing a character rotation code;

storing a binary representation of a terminator code to indicate that a current character has been completed;

testing a predetermined binary bit of said character rotation code for an odd integer multiple of forty-five degrees;

increasing said second binary number defining a number of matrix steps in a stroke by an integer multiple thereof if said testing step determines an odd integer multiple of forty-five degrees in said character rotation code.

2. A method of storing characters in a display system having a display device with an orthogonal matrix of addressable points and drawing said stored characters on said display device, comprising the storing steps of:

representing each character as a succession of strokes each constrained to lie in one of eight fundamental directions of the matrix, and, except for a first stroke, each starting at an end of a previous stroke;

storing each such stroke in a binary coded form which includes a first binary number defining an angular direction of said stroke, a second binary number defining a number of matrix steps from one point to a next point along said stroke, and a third binary number defining a visibility characteristic of said stoke;

storing a binary representation of a terminator code to indicate that a current character has been completed; and

storing a representation of a character string count; and

further comprising the drawing steps of;

accessing a character to be drawn;

determining a location in storage for a first stroke of said character to be drawn; and

further comprising the additional drawing steps of;

determining whether a binary code representing said stroke is a terminator code;

accessing a next character if said code is a terminator code;

determining whether a character rotation code is to be added to a direction code for said stroke;

if a character rotation code is to be added testing a predetermined binary bit of said character rotation code for an odd integer multiple of 45 degrees;

doubling said second binary number defining a number of matrix steps in a stroke if said testing step determines an odd integer multiple of 45 degrees in said character rotation code, drawing said stroke on a display device; and

determining a location in storage for a next stroke of said character to be drawn and repeating said additional drawing steps until all strokes of said character have been drawn and repeating said drawing steps until all characters have been drawn.