VIDEO PROCESSING

• US 20080056605A1
• Filed: 08/28/2007
• Published: 03/06/2008
• Est. Priority Date: 09/01/2006
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Chang, Weider, Shehata, Shereef
• Granted Patent: US 7,933,469 B2
• Time in Patent Office: Days
• US Class Current: 382/274
• CPC Class Codes: G06V 10/28 Quantising the image, e.g. histogram thresholding for discrimination between background and foreground patterns
• CPC Class Codes: G06V 10/56 relating to colour
• CPC Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence

Abstract

Digital video contrast enhancement and skin tone correction by conversio to CIECAM02 color space with lightness transformation and a skin tone probability density function of hue and saturation.

Claims

1. A color video local contrast enhancement method, comprising the steps of:

(a) receiving a frame of an input color video sequence with pixel color values in the CIECAM02 color space of J, h, and s values;

(b) for a pixel of said frame, computing a local contrast from J values of pixels in a window about said pixel;

(c) transforming said local contrast for said pixel to an enhanced local contrast for said pixel; and

(d) computing an enhanced J value for said pixel using said enhanced local contrast for said pixel together with said J values of pixels in said window about said pixel.

2. The method of claim 1, wherein said step (b) computing a local contrast finds the absolute value of said J value for said pixel minus a weighted average of said J values of pixels in said window.

3. The method of claim 1, wherein said local contrast and said enhanced local contrast are both confined to the range of values from 0 to 1, and said step (d) computing an enhanced J value includes multiplication of a weighted average of said J values of pixels in said window by the factor (1+x)/(1−

x) where x is either said enhanced local contrast or the negative of said enhanced local contrast.

4. A color video local contrast enhancer, comprising:

(a) an input for receiving a frame of a color video sequence with pixel color values in the CIECAM02 color space of J, h, and s values;

(b) a local contrast transformer coupled to said input and operable to transform said J values of said pixels to locally-contrast-enhanced J values from;

(i) a local contrast for a pixel computed from J values of pixels in a window about said pixel;

(ii) an enhanced local contrast for said pixel computed from said local contrast for said pixel; and

(iii) an enhanced J value for said pixel computed from said enhanced local contrast for said pixel together with said J values of pixels in said window about said pixel.