Method and apparatus for composing layered synthetic graphics filters

• US 6,072,501 A
• Filed: 06/27/1997
• Issued: 06/06/2000
• Est. Priority Date: 06/27/1997
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Bier, Eric A.
• Primary Examiner(s): Zimmerman, Mark K.
• Assistant Examiner(s): Lee, Albert K.
• Application Number:
  US08/883,845
• Time in Patent Office: 1,075 Days
• Field of Search: 345/433, 345/441, 345/434, 345/435
• US Class Current: 345/629
• CPC Class Codes: G06T 11/00 2D [Two Dimensional] image generation

Abstract

A computerized two-dimensional illustration system composes an image of a scene with layered synthetic graphics filters or lenses. The scene is defined by an ordered list of shapes. Some of the shapes in the ordered list of shapes are lenses. Each lens is a shape that has a fill color which is an operator rather than a constant. The operator of a selected lens performs a filtering function on the shapes ordered below it in the list of shapes. To compose a selected lens in the scene, the system first computes an under-list of shapes for the selected lens. The under-list of shapes is used to identify those shapes in the ordered list of shapes to which the filtering function of the selected lens may apply. Depending on the filtering function of a lens, the lens composes in either a back-to-front order or a front-to-back order. A lens composes in a back-to-front order by freezing lenses in the under-list before applying the filtering function of the lens to shapes in the under-list. In contrast, a lens composes in a front-to-back order by applying the filtering function of the lens to the under-list of shapes before freezing lenses in the under-list. When a lens is frozen, it is replaced with a cluster of shapes that are formed independently of other shapes in the list of shapes.

Claims

1. A method for composing an image with a computer illustration system, comprising the steps of:

defining a list of shapes in a memory;

specifying each of a plurality of shapes in the list of shapes to be a lens with a filtering function that applies to at least one other shape in the list of shapes;

assigning a composition order to each lens specified in the list of shapes to have one of a front-to-back ordering and a back-to-front ordering;

said assigning step assigning at least one of the lenses to have a front-to-back ordering and at least another of the lenses to have a back-to-front ordering; and

forming each shape in the list of shapes to compose the image.

2. The method according to claim 1, wherein said specifying step specifies the filtering function to be one of a scaling function and a tinting function.

3. The method according to claim 1, further comprising the step of limiting the scope of operation of a selected lens in the list of shapes to exclude at least one of the shapes in the list of shapes from being modified by the filtering function of the selected lens.

4. The method according to claim 3, further comprising the step of defining a cluster of shapes that includes the selected lens and at least one other shape in the list of shapes.

5. The method according to claim 4, wherein said limiting step limits the scope of operation of the selected lens by excluding those shapes outside the cluster of shapes from being modified by the filtering function of the lens.

6. The method according to claim 4, wherein said limiting step limits the scope of operation of the selected lens by excluding those shapes inside the cluster of shapes from being modified by the filtering function of the lens.

7. The method according to claim 3, wherein said limiting step further comprises the step of combining several non-overlapping lenses into a single lens with multiple regions.

8. The method according to claim 1, wherein said forming step forms each lens in the list of shapes by:

computing an under-list of shapes for the selected lens;

the under-list of shapes identifying shapes in the list of shapes to which the filtering function of the selected lens may apply;

freezing any shape specified to be a lens in the under-list of shapes by replacing each lens with shapes that are formed independently of other shapes; and

applying the filtering function of the selected lens to each shape in the under-list of shapes.

9. The method according to claim 8, wherein said freezing step is performed before said applying step when the composition order of a lens is assigned a back-to-front ordering.

10. The method according to claim 8, wherein said applying step is performed before said freezing step when the composition order of a lens is assigned a front-to-back ordering.

11. The method according to claim 8, further comprising the step of copying each shape in the under-list before said freezing step and said applying step are performed.

12. A computer illustration system for composing an image, comprising:

a memory for storing a list of shapes;

means for specifying each of a plurality of shapes in the list of shapes to be a lens with a filtering function that applies to at least one other shape in the list of shapes;

means for assigning a composition order to each lens specified in the list of shapes to have one of a front-to-back ordering and a back-to-front ordering;

said assigning means assigning at least one of the lenses to have a front-to-back ordering and at least another of the lenses to have a back-to-front ordering; and

processing means for forming each shape in the list of shapes to compose the image.

13. The computer illustration system according to claim 12, wherein said processing means composing a selected lens specified in the list of shapes by:

computing an under-list of shapes for the selected lens;

the under-list of shapes identifying shapes in the list of shapes to which the filtering function of the selected lens may apply;

freezing each lens in the under-list of shapes by replacing each lens with shapes that are formed independently of other shapes in the list of shapes; and

applying the filtering function of the selected lens to each shape in the under-list of shapes.

14. The computer illustration system according to claim 13, wherein said processing means freezes each lens in the under-list of shapes before applying the filtering function of the selected lens to each shape in the under-list of shapes.

15. The computer illustration system according to claim 13, wherein said processing means applies the filtering function of the selected lens to each shape in the under-list of shapes before freezing each lens in the under-list of shapes.

16. The computer illustration system according to claim 13, further comprising means for copying each shape in the under-list before freezing each lens in the under-list of shapes and applying the filtering function of the selected lens to each shape in the under-list of shapes.

17. The computer illustration system according to claim 12, wherein said processor limits the scope of operation of the lens of the first object to exclude at least one of the shapes layered below the lens from being modified by the filtering function of the lens.

18. The computer illustration system according to claim 17, wherein said processor defines a cluster of shapes that includes the lens in the list of shapes and selected shapes in the list of shapes layered below the lens.

19. The computer illustration system according to claim 18, wherein said processor limits the scope of operation of the lens by excluding those shapes outside the cluster of shapes from being modified by the filtering function of the lens.

20. The computer illustration system according to claim 18, wherein said processor limits the scope of operation of the lens by excluding those shapes inside the cluster of shapes from being modified by the filtering function of the lens.

21. The computer illustration system according to claim 18, wherein said processor further comprises means for combining several non-overlapping lenses into a single lens with multiple regions.