Method and apparatus for correcting preferred color and liquid crystal display device using the same

• US 8,160,356 B2
• Filed: 06/23/2008
• Issued: 04/17/2012
• Est. Priority Date: 06/25/2007
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Ahn, Ji Young, Kang, Dong Woo, Kim, Choon Woo, Kim, Kyoung Tae
• Primary Examiner(s): Wu, Jingge
• Application Number:
  US12/213,669
• Publication Number:
  US 20080317340A1
• Time in Patent Office: 1,394 Days
• Field of Search: 382162-167, 358518-540
• US Class Current: 382/167
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence
• CPC Class Codes: H04N 1/6075 Corrections to the hue
• CPC Class Codes: H04N 9/643 Hue control means, e.g. flesh tone control
• CPC Class Codes: H04N 9/67 for matrixing camera processing pipelines for matrixing of colour signals H04N23/85

Abstract

A method and apparatus for correcting a preferred color, which is capable of correcting the preferred color in consideration of an input image and the visual characteristics of a person by correcting differences between colors preferred by the person and an average color coordinate of a color to be corrected in the input image, and a liquid crystal display device using the same are disclosed. The method for correcting a preferred color includes converting data of an input image into lightness (L), chroma (C) and hue (H) data, detecting a preferred-color pixel from the input image, calculating average values of the L, C and H data of the preferred-color pixel, correcting the C and H data of the preferred-color pixel according to differences between the average values of the C and H data and reference values of the C and H data, correcting the L data of the preferred-color pixel according to the average value of the L data according to the hue of the preferred-color pixel, and inversely converting the corrected L, C and H data into image data.

Claims

1. A method for correcting a preferred color, the method comprising:

converting data of an input image into lightness (L), chroma (C) and hue (H) data;

detecting a preferred-color pixel from the input image;

calculating average values of the L, C and H data of the preferred-color pixel;

correcting the C data of the preferred-color pixel according to a difference between the C average values of the corresponding preferred-color pixel and a predetermined C reference value of the corresponding preferred-color pixel;

correcting the H data of the preferred-color pixel according to a difference between the H average values of the corresponding preferred-color pixel and a predetermined H reference value of the corresponding referred-color pixel;

correcting the L data of the preferred-color pixel according to the L average value of the preferred-color pixel or not according to the hue of the preferred-color pixel; and

inversely converting the corrected L, the corrected C and the corrected H data into image data according to the hue of the preferred-color pixel or inversely converting the non-corrected L, the corrected C and the corrected H data into image data according to the hue of the preferred-color pixel.

2. The method according to claim 1, wherein the detecting of the preferred-color pixel comprises:

comparing the H data of the input pixel with a reference range of the H data of the preferred color and detecting a first preferred-color pixel; and

performing a best linear estimation (BLE) operation of the first preferred-color pixel and detecting a second preferred-color pixel.

3. The method according to claim 2, wherein the detecting of the second preferred-color pixel comprises:

calculating a preferred-color discrimination constant by a matrix product of an input matrix composed of characteristic data of the first preferred-color pixel and a weight vector matrix composed of weight vectors of the preferred color; and

comparing the calculated preferred-color discrimination constant with a reference range of the preferred-color discrimination constant and detecting the second preferred-color pixel.

4. The method according to claim 3, wherein each of the correcting of the C and H data comprises:

calculating a correction function for compensating for the differences between the C or H average value and the C or H reference value of the preferred-color pixel;

calculating a weighting function for adjusting a peak value of the C or H average value of the preferred-color pixel;

multiplying the correction function by the weighting function and calculating a final correction function;

calculating correction amounts of the C or H data of the preferred-color pixel using the final correction function; and

compensating for the C or H data of the preferred-color pixel by the correction amounts.

5. The method according to claim 4, wherein the correcting of the L data is performed only if the hue of the preferred-color pixel is a skin-color.

6. The method according to claim 5, wherein the correcting of the L data of the skin-color pixel comprises:

calculating an L correction function according to the L average value the skin-color pixel;

calculating an L correction amount according to the L data using the L correction function; and

compensating for the L data of the skin-color pixel by the L correction amount.

7. The method according to claim 6, further comprising compensating for the L data of all pixels of the input image by the L correction amount of the skin-color pixel.

8. The method according to claim 4, further comprising:

calculating a secondary weighting function for decreasing the correction amount in a boundary of the preferred-color pixel using the preferred-color discrimination constant of the second preferred-color pixel used in the detecting of the preferred-color pixel; and

multiplying the secondary weighting function by the final correction function.

9. An apparatus for correcting a preferred color, the apparatus comprising:

a color coordinate converter which converts data of an input image into lightness (L), chroma (C) and hue (H) data;

a preferred-color detector which detects a preferred-color pixel from the input image;

an LCH average value calculator which calculates average values of the L, C and H data of the preferred-color pixel from the preferred-color detector;

a preferred-color corrector which corrects the C data of the preferred-color pixel according to a difference between the C average of the corresponding preferred-color pixel and a predetermined C reference value of the corresponding preferred-color pixel, corrects the H data of the preferred-color pixel according to a difference between the H average values of the corresponding preferred-color pixel and a predetermined H reference value of the corresponding preferred-color pixel, and corrects the L data of the preferred-color pixel according to the L average value of the preferred-color pixel or not according to the hue of the preferred-color pixel; and

a color coordinate inverse-converter which inversely converts the corrected L, the corrected C and the corrected H data from the preferred-color corrector into image data according to the hue of the preferred-color pixel or inversely converts the non-corrected L, the corrected C and the corrected H data into image data according to the hue of the preferred-color pixel.

10. The apparatus according to claim 9, wherein the preferred-color detector compares the H data from the color coordinate converter with a reference range of the H data of the preferred color so as to detect a first preferred-color pixel, calculates a preferred-color discrimination constant by a matrix product of an input matrix composed of characteristic data received from the color coordinate converter with respect to the first preferred-color pixel and a weight vector matrix composed of weight vectors of the preferred color, and compares the calculated preferred-color discrimination constant with a reference range of the preferred-color discrimination constant so as to detect the second preferred-color pixel.

11. The apparatus according to claim 10, wherein the preferred-color corrector calculates a correction function for compensating for the differences between the C and H average values and the C and H reference values and a weighting function for adjusting peak values of the C and H average values, multiplies the correction function by the weighting function so as to calculate a final correction function, calculating calculates correction amounts of the C and H data using the final correction function, and compensates for the C and H data by the correction amounts.

12. The apparatus according to claim 11, wherein the preferred-color corrector calculates an L correction function according to the L average value of the skin-color pixel, calculates an L correction amount according to the L data using the calculated L correction function, and compensates for the L data of the skin-color pixel by the L correction amount, if the second preferred-color pixel is a skin-color pixel.

13. The apparatus according to claim 12, wherein the preferred-color corrector compensates for the L data of all pixels of the input image by the L correction amount of the skin-color pixel.

14. The apparatus according to claim 11, wherein the preferred-color corrector calculates a secondary weighting function for decreasing the correction amount in a boundary of the preferred-color pixel using the preferred-color discrimination constant of the second preferred-color pixel used in the preferred-color detector, and multiplying the calculated secondary weighting function by the final correction function.

15. A liquid crystal display device which displays the image data output from the apparatus for correcting the preferred color according to any one of claims 9 to 14 on a liquid crystal panel.