Television signal chrominance adjustment

• US 6,400,371 B1
• Filed: 05/18/1998
• Issued: 06/04/2002
• Est. Priority Date: 05/16/1997
• Status: Expired due to Term

• Current Assignee: Comcast Cable Communications Management LLC (Comcast Corporation)
• Original Assignee: Liberate Technologies
• Inventors: Helman, James, Yu, Chee, Mott, David
• Primary Examiner(s): Luu, Matthew
• Assistant Examiner(s): Sajous, Wesner
• Application Number:
  US09/081,486
• Time in Patent Office: 1,478 Days
• Field of Search: 348/577, 348/587, 348/592, 348/630, 348/631, 348/650, 348/708, 348/254, 348/283, 348/645, 348/649, 348/602-603, 348/658, 348/191, 345/589-592, 345/597, 345/593, 345/114, 345/150, 345/157, 345/507, 345/509, 345/419, 345/433, 345/436, 345/473, 382/162, 382/164, 382/165, 382/283, 382/238, 709/218-220
• US Class Current: 345/589
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2370/027 Arrangements and methods specific for the display of internet documents
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response
• CPC Class Codes: H04N 9/77 Circuits for processing the brightness signal and the chrominance signal relative to each other, e.g. adjusting the phase of the brightness signal relative to the colour signal, correcting differential gain or differential phase circuits for matrixing H04N9/67

Abstract

The invention provides an improved method and system for presenting color television signals. Television signal chrominance values for foreground elements are adjusted in response to television signal chrominance values for background elements, so as to minimize display artifacts while preserving the relative color contrast between foreground and background. (1) The invention modifies I and Q values of the foreground color to reduce the difference of the foreground I and Q with respect to the background I and Q. (2) The invention modifies Y, I and Q values of the foreground color to avoid colors known to display poorly for selected output devices. (3) The invention modifies Y values of the foreground color to maintain intended visual contrast between foreground and background colors. (4) The invention modifies Y, I and Q values of the foreground color to decrease cross-luminance separation artifacts at the border between foreground and background colors.

Claims

1. A system for modifying color video signals representing a visual image for display on a television, said system comprising:

a color recognizer for recognizing foreground and background colors in the visual image;

a color modifier for modifying luminance and chrominance of said foreground colors in response to the recognized foreground and background colors;

wherein the visual image comprises a document generated in HTML, and said color modifier is further responsive to HTML codes in said document.

2. A system for modifying color video signals representing a visual image for display on a television, said system comprising:

a color recognizer for recognizing foreground and background colors in the visual image;

a color modifier for modifying luminance and chrominance of said foreground colors in response to the recognized foreground and background colors;

wherein the visual image comprises a document generated in HTML, and said color modifier is further responsive to controls in a web browser responsive to said document.

3. A system for modifying color video signals representing a visual image for display on a television, said system comprising:

a color recognizer for recognizing foreground and background colors in the visual image;

a color modifier for modifying luminance and chrominance of said foreground colors in response to the recognized foreground and background colors;

wherein the visual image comprises a document generated in HTML, and said color modifier is further responsive to the visual content of said document.

4. A system for modifying color video signals representing a visual image for display on a television, said system comprising:

a color recognizer for recognizing foreground and background colors in the visual image;

a color modifier for modifying luminance and chrominance of said foreground colors in response to the recognized foreground and background colors;

wherein said color modifier is further responsive to control codes generated by the television.

5. The system of claim 4 wherein said control codes can be modified by the television user.

6. A method of modifying color video signals representing a visual image for display on a television, said method comprising:

recognizing foreground and background colors in the visual image; and

modifying chrominance and luminance of said foreground colors in response to the recognized foreground and background colors;

wherein the visual image comprises a document generated in HTML, and said step of modifying said foreground color further comprises responding to HTML codes in said document.

7. A method of modifying color video signals representing a visual image for display on a television, said method comprising:

recognizing foreground and background colors in the visual image; and

modifying chrominance and luminance of said foreground colors in response to the recognized foreground and background colors;

wherein the visual image comprises a document generated in HTML, and said step of modifying said foreground color further comprises responding to controls in a web browser for viewing said document.

8. A method of modifying color video signals representing a visual image for display on a television, said method comprising:

recognizing foreground and background colors in the visual image; and

modifying chrominance and luminance of said foreground colors in response to the recognized foreground and background colors;

wherein the visual image comprises a document generated in HTML, and said step of modifying said foreground color further comprises responding to the visual content of said document.

9. A method of modifying color video signals representing a visual image for display on a television, said method comprising:

recognizing foreground and background colors in the visual image; and

modifying chrominance and luminance of said foreground colors in response to the recognized foreground and background colors;

wherein said step of modifying said foreground color further comprises responding to control codes generated by the television.

10. The method of claim 9 wherein said control codes may be modified by the television user.