Pointer-based computer system capable of aligning geometric figures

• US 5,621,817 A
• Filed: 04/13/1995
• Issued: 04/15/1997
• Est. Priority Date: 05/27/1992
• Status: Expired due to Term

• Current Assignee: Apple Computer Incorporated (Apple Inc.)
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Bozinovic, Radmilo, Pagallo, Giulia
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): Tadayon, Bijan
• Application Number:
  US08/422,130
• Time in Patent Office: 733 Days
• Field of Search: 382/173, 382/187, 382/197, 382/199, 382/201, 382/202, 382/203, 382/224, 382/189, 382/175, 382/181, 382/186, 382/188, 382/190, 382/192, 382/195, 382/204, 382/205, 382/217 , 382/282, 382/284, 382/286, 382/287, 382/288, 382/289, 382/290, 382/291, 382/292, 382/293, 382/294, 382/295, 382/296, 382/308, 382/309, 345/133, 345/179, 345/173, 345/156
• US Class Current: 382/189
• 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 pointer-based computer system capable of aligning geometric figures in clusters, the system comprising:

a display screen sensitive to the location of a pointer;

a stroke grouper receptive to a plurality of strokes formed on the display screen by the pointer and operative to group the plurality of strokes into a stroke group;

a shape recognition engine receptive to the stroke group and capable of recognizing said stroke group as a geometric figure taken form the classes of at least one of circles and squares;

means for determining the value of an alignment parameter for a new geometric figure provided to the display screen;

means for determining, for a cluster of geometric figures on said display screen, a fixed value for the alignment parameter, a mean value of the alignment parameter, and a variance from the mean value for geometric figures making up the cluster;

means for determining whether the alignment parameter of the new geometric figure added to the display screen is within a defined threshold distance of the cluster'"'"'s mean value;

means for aligning the new geometric figure with the cluster on the display screen such that the new geometric figure is aligned with the fixed value of the cluster; and

means for redefining the cluster'"'"'s mean value and variance from the mean for new geometric figures making up the cluster to account for the addition of the new shape to the cluster.

2. The pointer-based computer system of claim 1 wherein the pointer is a stylus.

3. The pointer-based computer system of claim 1 wherein the means for determining the value of the alignment parameter determines, for the new geometric figure, the value of a parameter selected from the group consisting of coordinates and sizes of the new geometric figure.

4. The pointer-based computer system of claim 1 wherein the means for determining, for a cluster of geometric figures on said display screen, a fixed value for the alignment parameter, a mean value of the alignment parameter, and a variance from the mean value for geometric figures making up the cluster

sets the fixed value of the cluster'"'"'s alignment parameter equal to the alignment parameter of the first shape added to the cluster.

5. The pointer-based computer system of claim 1 wherein the means for determining the value of the alignment parameter of the new geometric figure determines the value of the alignment parameter for circles and squares added to the screen.

6. The pointer-based computer system of claim 1 wherein the means for aligning the new geometric figure with the cluster displays the new geometric figure as if the value of its alignment parameter was equal to the fixed value for the cluster.

7. The pointer-based computer system of claim 1 wherein the means for determining whether the alignment parameter of the new geometric figure added to the display screen is within a defined threshold distance determines whether the new figure'"'"'s alignment parameter lies within a range of alignment parameters of the shapes constituting the cluster.

8. A pointer-based computer system capable of aligning geometric figures in clusters, the system comprising:

a display screen sensitive to the location of a pointer;

a shape recognition engine receptive to a stroke group formed on the display screen by the pointer, the shape recognition engine also being capable of recognizing said stroke group as a geometric figure taken from the classes of at least one of circles and squares;

means for determining the value of an alignment parameter for a new geometric figure provided to the display screen;

means for determining whether the alignment parameter of the new geometric figure is within a defined threshold distance of a corresponding alignment parameter for another geometric figure or a cluster of geometric figures on said display screen; and

means for aligning the new geometric figure with the other geometric figure or cluster on the display screen.

9. The pointer-based computer system of claim 8 further comprising means for determining, for a cluster of geometric figures on said display screen, a fixed value for the alignment parameter, a mean value of the alignment parameter, and a variance from the mean value for geometric figures making up the cluster.

10. The pointer-based computer system of claim 8 wherein the pointer is a stylus.

11. The pointer-based computer system of claim 8 wherein the means for determining the value of the alignment parameter for the new geometric figure determines, for the new geometric figure, the value of a parameter selected from the group consisting of coordinates and sizes of the new geometric figure.

12. The pointer-based computer system of claim 8 wherein the means for determining the value of the alignment parameter for the new geometric figure determines the value of the alignment parameter for circles and squares added to the screen.

13. The pointer-based computer system of claim 8 wherein the means for determining whether the alignment parameter of the new geometric figure added to the display screen is within a defined threshold distance determines whether the new figure'"'"'s alignment parameter lies within a range of alignment parameters of the other geometric figure or the geometric figures constituting the cluster.