Method for editing character bit maps at small sizes using connected runs

• US 5,255,357 A
• Filed: 05/25/1993
• Issued: 10/19/1993
• Est. Priority Date: 07/13/1990
• Status: Expired due to Term

• Current Assignee: Adobe Systems Incorporated (Adobe Inc.)
• Original Assignee: Adobe Systems Incorporated (Adobe Inc.)
• Inventors: Byron, Michael, Malloy, Thomas
• Primary Examiner(s): Harkcom, Gary V.
• Assistant Examiner(s): Feild, Joseph H.
• Application Number:
  US08/067,333
• Time in Patent Office: 147 Days
• Field of Search: 395/150, 395/151, 340/728, 340/730, 340/731, 340/735, 382/47, 382/54
• US Class Current: 345/170
• CPC Class Codes: G06K 15/02 using printers
• CPC Class Codes: G06K 2215/0045 Converting outline to bitmap
• CPC Class Codes: G09G 5/24 Generation of individual character patterns
• CPC Class Codes: Y10S 345/947 Font character edge processing
• CPC Class Codes: Y10S 345/948 Alteration of stored fonts to maintain feature consistency throughout scaled font

Abstract

A material of displaying a character on a raster device wherein the character is described by means of one or more paths. The crosses where a path intersects horizontal pixel midlines are identified and paired in scan line order as cross pairs. Runs of pixels are identified from the cross pairs. Collisions are identified between two runs of pixels and the repair operation is performed to remove the collision while maintaining the integrity of the character. The most common repair operation is to move or delete one or more of the pixels involved in the collision.

Claims

1. In a method of displaying a character having one or more black areas in the form of a plurality of pixels on a raster device which generates a plurality of horizontal scan lines in sequential order, wherein the character is described by an outline comprising one or more path segments;

a cross is defined by the intersection of the character outline with the horizontal midline of a pixel;

a cross pair is defined by two crosses which reside on the same scan line;

runs of pixels are identified as the pixels between the two crosses of a cross pair, an improvement comprising the steps of;

identifying where two of said runs collide with each other to cause a collision, and repairing the character by eliminating said collision between said two runs of pixels while maintaining the integrity of the character.

2. The improvement of claim 1 wherein said collision is between two runs on the same scan line which overlap.

3. The improvement of claim 1 wherein the step of identifying said collision includes the steps of:

(1) identifying a path segment whose endpoints occur at the locations defined by two crosses, both on the same scan line, and where the leftmost of said two crosses is the leftmost cross of its respective cross pair and the rightmost of said two crosses is the rightmost cross of its respective cross pair;

(2) for each cross pair containing at least one of said two crosses, identifying the scan line adjacent to said same scan line and lying on the same side of said two crosses as said path segment; and

(3) identifying runs of pixels in said adjacent scan line that touch said first run, thereby creating one or more collisions.

4. The improvement of claim 1 wherein said collision is where said two runs are black and are not adjacent in path order by touch at a corner.

5. The improvement of claim 1 wherein said collision to be repaired is between runs on the same scan line, said runs touching each other at one edge but not overlapping.

6. The improvement of claim 1 wherein a collision is defined by two runs of pixels, and wherein each of said runs of pixels has a pixel which touches a pixel of the other run, wherein said collision identification step includes identifying the touching pixels as two trespassers, the first trespasser having neighbor pixels, and wherein the repairing step includes deleting or moving a first of said trespassers based on the relative configuration of said first trespasser, its neighbor pixels and the said second trespasser.

7. The improvement of claim 6 wherein said relative configuration of said first trespasser, the neighbor pixels of said first trespasser and said second trespasser is evaluated on a three by three matrix having a pixel in each matrix cell, wherein said first trespasser is in the center cell of said matrix.

8. The improvement of claim 1 wherein said repairing step comprises moving or deleting a pixel in one of said runs.

9. The improvement of claim 8 wherein said repairing step moves one or more pixels.

10. The improvement of claim 1 wherein said collision to be repaired is a collision between two runs on different scan lines, each run having a pixel which touches a pixel in the other run at one corner.

11. The improvement of claim 1 wherein said collision to be repaired is a collision between two runs on different scan lines, each run having a pixel which touches a pixel in the other run at one edge and wherein at least one of said pixel runs is only one pixel wide.

12. The improvement of claim 1 wherein said collision to be repaired is a collision between two runs on the same scan line, each of said two runs having a pixel which touches a pixel on the other run on one edge.