Real time programmable chroma keying with shadow generation

• US 7,006,155 B1
• Filed: 02/01/2000
• Issued: 02/28/2006
• Est. Priority Date: 02/01/2000
• Status: Expired due to Fees

• Current Assignee: Cadence Design Systems Incorporated (Cadence Group)
• Original Assignee: Cadence Design Systems Incorporated (Cadence Group)
• Inventors: Tse, Clement, Agarwala, Vinay
• Primary Examiner(s): Kostak, Victor R.
• Application Number:
  US09/495,540
• Time in Patent Office: 2,219 Days
• Field of Search: 348590-599, 348/578, 348/584, 348/187, 348/587, 358/22, 345/634, 345/637, 345/639, 345/640, 345/589, 345/591, 345/592
• US Class Current: 348/592
• CPC Class Codes: H04N 5/272 Means for inserting a foreground image in a background image, i.e. inlay, outlay
• CPC Class Codes: H04N 5/275 Generation of keying signals
• CPC Class Codes: H04N 9/75 Chroma key

Abstract

A system for forming composite video images from one or more foreground images and one or more background images. In one embodiment, s sum of a suppressed foreground image signal with weight α, with one or more selected foreground colors suppressed, and a background image signal with weight 1−α′ (0≦α′≦1) is formed, where a and α′ may vary from pixel to pixel and with time. In another embodiment, a shadow from a selected foreground image is impressed on selected pixels of a background image. In another embodiment, foreground suppression and shadowing are combined, optionally by retrofitting, using an existing α-mixer or a newly constructed α-mixer. Provision of a chroma key map allows a foreground image shadow to be prescribed pixel by pixel, including a transition region in which the shadowed image slowly disappears.

Claims

1. Apparatus for formation of a composite video image, the apparatus comprising:

a shadow control module that receives a foreground video image signal and generates a shadow key that identifies at least one selected pixel for which foreground shadowing is activated;

a shadow generation module that receives the foreground image signal and the shadow key and generates and issues a foreground shadow signal FGSh, in which each selected pixel appears in a shadow format; and

a shadowing module that receives the foreground shadow signal and a background video image signal BG and generates a modified background image signal, in which a foreground shadow is impressed on each selected pixel of the background image, wherein said shadowing module forms a sum signal β

·

FGSh+(1−

β

′

)·

BG, as said modified background image signal, where β and

β

′

are real numbers lying in a range [0,1], selected so as to limit either an intensity of the foreground shadow or an intensity of the background image, wherein β

is less than β

′

thereby limiting the intensity of the background image.

2. An apparatus for formation of a composite video image, the apparatus comprising:

a shadow control module that receives a foreground video image signal and generates a shadow key that identifies at least one selected pixel for which foreground shadowing is activated;

a shadow generation module that receives the foreground image signal and the shadow key and generates and issues a foreground shadow signal FGSh, in which each selected pixel appears in a shadow format; and

a shadowing module that receives the foreground shadow signal and a background video image signal BG and generates a modified background image signal, in which a foreground shadow is impressed on each selected pixel of the background image, wherein said shadowing module forms a sum signal β

·

FGSh+(1−

β

′

)·

BG, as said modified background image signal, where β and

β

′

are real numbers lying in a range [0,1], selected so as to limit either an intensity of the foreground shadow or an intensity of the background image, wherein β

is greater than β

′

thereby limiting the intensity of the foreground shadow.

3. A method for formation of a composite video image, the method comprising:

receiving a foreground video image signal and generating a shadow key that identifies at least one selected pixel for which foreground shadowing is activated;

receiving the foreground image signal and the shadow key and generating and issuing a foreground shadow signal, FGSh, in which each selected pixel appears in a shadow format; and

receiving the foreground shadow signal and a background video image signal BG and generating a modified background image signal, MBG, in which a foreground shadow is impressed on each selected pixel of the background image by forming a sum signal, β

·

FGSh+(1−

β

′

)·

BG, as a modified background image signal, where β and

β

′

are real numbers lying in a range [0,1], selected so as to limit either an intensity of the foreground shadow or an intensity of the background image, wherein β

is less than β

′

thereby limiting the intensity of the background image.

4. A method for formation of a composite video image the method comprising:

receiving foreground video image signal and generating a shadow key that identifies at least one selected pixel for which foreground shadowing is activated;

receiving the foreground image signal and the shadow key and generating and issuing a foreground shadow signal, FGSh, in which each selected pixel appears in a shadow format; and

receiving the foreground shadow signal and a background video image signal BG and generating a modified background image signal, MBG, in which a foreground shadow is impressed on each selected pixel of the background image by forming a sum signal, β

·

FGSh+(1−

β

′

)·

BG, as a modified background image signal, where β and

β

′

are real numbers lying in a range [0,1], selected so as to limit either an intensity of the foreground shadow or an intensity of the background image, wherein β

is greater than β

′

thereby limiting the intensity of the foreground shadow.

5. An article of manufacture comprising:

a computer usable medium having computer readable code means embodied therein for producing a composite video image including portions of at least one foreground image and of at least one background image;

computer readable program code means for receiving a foreground video image signal FG and generates a shadow key that identifies at least one selected pixel for which foreground shadowing is activated;

computer readable program code means for receiving the foreground image signal and the shadow key and generating and issues a foreground shadow signal FGSh, in which each selected pixel appears in a shadow format; and

computer readable program code means for receiving the foreground shadow signal and a background video image signal BG and generating a modified background image signal, in which a foreground shadow is impressed on each selected pixel of the background image by forming a sum signal β

·

FGSh+(1−

β

′

)·

BG as said modified background image signal, where β and

β

′

are selected real numbers lying in a range [0,1], selected so as to limit either an intensity of the foreground shadow or an intensity of the background image, wherein β

is greater than β

′

thereby limiting the intensity of the foreground shadow.

6. An article of manufacture comprising:

a computer usable medium having computer readable code means embodied therein for producing a composite video image including portions of at least one foreground image and of at least one background image;

computer readable program code means for receiving a foreground video image signal FG and generates a shadow key that identifies at least one selected pixel for which foreground shadowing is activated;

computer readable program code means for receiving the foreground image signal and the shadow key and generating and issues a foreground shadow signal FGSh, in which each selected pixel appears in a shadow format; and

computer readable program code means for receiving the foreground shadow signal and a background video image signal BG and generating a modified background image signal, in which a foreground shadow is impressed on each selected pixel of the background image by forming a sum signal β

·

FGSh+(1−

β

′

)·

BG as said modified background image signal, where β and

β

′

are selected real numbers lying in a range [0,1] selected so as to limit either an intensity of the foreground shadow or an intensity of the background image, wherein β

is less than β

′

thereby limiting the intensity of the background image.