Method of aligning shapes on a display of a computer system

• US 5,452,371 A
• Filed: 01/12/1994
• Issued: 09/19/1995
• Est. Priority Date: 05/27/1992
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Pagallo, Giulia, Bozinovic, Radmilo
• Primary Examiner(s): Couso, Jose L.
• Application Number:
  US08/180,559
• Time in Patent Office: 615 Days
• Field of Search: 382/9, 382/13, 382/21-25, 382/36, 395/144-146, 395/155, 345/121
• US Class Current: 382/187
• CPC Class Codes: G06V 30/347 Sampling; Contour coding; Stroke extraction

Abstract

An apparatus for recognizing shapes characterized by a stroke grouper receptive to a plurality of strokes formed on a screen of a pen-based computer system; a shape recognition engine receptive to a stroke group produced by the stroke grouper; and a knowledge base coupled to the shape recognition engine, where the knowledge base includes, at a minimum, knowledge concerning closed polygons and closed curves. Preferably, the closed curves of the knowledge base include both circles and ellipses. A method for recognizing digitized shapes in a computer system includes the steps of receiving at least one user-initiated stroke; grouping the user-initiated stroke with related strokes to form a stroke group; and analyzing the stroke group to make a best-guess shape represented by the stroke group. Preferably, the method also looks for other shapes which are related to the best-guess shape and modifying at least one of the location, size, or shape of the best-guess shape to conform with the other shapes. The strokes are typically grouped when they are related in time, or space, or in both time and space. A method for recognizing and forming shapes includes the steps of: creating a live group including at least one live stroke; characterizing shape sides from the live group, where a shape side is either straight or curved; forming a polygon from the shape sides if all the shape sides are straight; forming an ellipse from the shape sides if all the shape sides are curved; and forming a composite curve from the shape sides if the shape sides are a mixture of straight sides and curved sides. The step of characterizing shape sides preferably includes the steps of: finding kinks in the live group; defining shape sides as segments between the kinks; and determining whether the shape sides are straight or curved.

Claims

1. A method, implemented on a computer system, of arranging shapes on a display screen of a computer system such that some shapes added to the display screen are aligned with respect to existing shapes already present on the display screen, said shapes being created by the interaction of a pointer with the display screen and said shapes each having an alignment parameter, said existing shapes also being grouped into one or more clusters, the method comprising the following steps:

determining the value of the alignment parameter for each shape added to the display screen;

defining for each cluster a fixed value for the alignment parameter, a mean, value of the alignment parameter, and a variance from the mean value for the shapes making up the cluster;

determining whether the value of a new shape'"'"'s alignment parameter is within a defined threshold distance of any cluster'"'"'s mean value;

if the new shape'"'"'s alignment parameter is within said defined threshold distance of a close cluster'"'"'s mean value, adding the new shape to that cluster such that the new shape is aligned with the fixed value of the close cluster; and

redefining the mean value of the alignment parameter and the variance from the mean for the shapes making up the close cluster to account for the addition of the new shape to the close cluster wherein said steps of determining, defining, adding, and redefining are performed by said computer system.

3. The method of claim 1 wherein the step of determining the value of the alignment parameter for each shape added to the display screen includes a step of determining a coordinate or size of each shape.

4. The method of claim 1 wherein the step of determining the value of the alignment parameter for each shape added to the display screen involves determining the value of the alignment parameter for circles and squares added to the screen.

5. The method of claim 1 wherein the step of aligning the new shape with the fixed value of the close cluster involves displaying the new shape as if the value of its alignment parameter was equal to the fixed value for the close cluster.

6. The method of claim 1 wherein the step of determining whether the value of a new shape'"'"'s alignment parameter is within a defined threshold distance of any cluster'"'"'s center includes a step of determining whether the new shape'"'"'s alignment parameter lies within the range of alignment parameters of the shapes constituting any of the clusters.

2. The method of 1 wherein the step of defining a fixed value for the alignment parameter includes a step of setting the fixed value of each cluster'"'"'s alignment parameter equal to the alignment parameter of the first shape added to the cluster.