Method and apparatus for the automatic generation of subject to background transition area boundary lines and subject shadow retention
US6667774B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 2, 2001 |
| Grant date | Dec 23, 2003 |
| Priority date | — |
| Expiry date | Nov 2, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/75
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Changes in a current image frame from variations in room light level, and automatic camera adjustments, are determined and incorporated into a clear (reference) frame, thereby resulting in a zero difference in the background region when the clear frame and a current frame are subtracted. Any deviation from zero defines the beginning edge of a transition from background to subject. The location of the outer edge of a transition area is further refined by subtracting derivatives of the RGB signals in each frame, and by the use of a fourth color channel when available. The difference of derivitives (dcu-dcl) identifies the subject to background transition area, whose edges define the inner and outer boundary lines. Shadow areas on the backing are retained and may be transferred to the inserted background scene. Small areas on the backing having the same color and luminance as the subject are prevented from printing through the subject by a second “derivative” alpha channel for the small areas.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.