Device and method for processing color image data
View Patent ↗The present invention relates to a video processing device comprising a luminance and saturation detector (LSHD) for detecting the luminance values (lum) and the saturation values (sat) of pixels of an input video signal (IN); and a white-point, saturation and hue modulator (WSH) for transforming luminance and saturation properties (lum, sat) of the pixels of the input video signal (IN) into white-point, saturation and hue correction factors (W, Wc; S, Sc; H, Hc). The video device also comprises a color gamut matrix generating unit (CGMG) for generating a color gamut matrix in the perception domain based on the white-point, saturation and hue correction factors (Wc, Sc, Hc) of the white-point, saturation and hue modulator (WSH); a color gamut mapping unit ( 20 ) for multiplying the pixels of the input video signal (IN) with a color gamut matrix generated by the color gamut matrix generating unit (CGMG); and a clipping unit ( 31 ) for clipping the results of the a color gamut mapping unit ( 20 ) which are out of a predefined range.
1. A video processing device, comprising:
a luminance and saturation detector adapted to detect the luminance values and the saturation values of pixels of an input video signal, wherein the luminance and saturation detector includes:
a RGB squaring unit adapted to square amplitudes of sub-pixels of the pixels of the input video signal,
a RGB shuffler unit adapted to rank the sub-pixels based on the respective squared amplitude values of the sub-pixels,
a luminance and saturation calculation unit adapted to calculate, for each pixel, the luminance value, an internal saturation and a first saturation correction factor, and
a saturation correction unit adapted to output the saturation value for each pixel, wherein said saturation value for said pixel is a corrected saturation value based on said internal saturation and the first saturation correction factor;
a white-point, saturation and hue modulator adapted to transform the luminance and saturation values of each pixel of the input video signal into a corresponding white-point correction factor, a second saturation correction factor, and a hue correction factor;
a color gamut matrix generating unit adapted to generate a color gamut matrix in the perception domain based on the white-point correction factor, the second saturation correction factor, and the hue correction factor;
a color gamut mapping unit adapted to multiply the pixels of the input video signal with the color gamut matrix; and
a clipping unit adapted to clip the results of the color gamut mapping unit which are out of a predefined range.
2. The video processing device according to claim 1 , wherein the white-point, saturation and hue modulator comprises:
a white point modulator adapted to determine, for each pixel, the white-point correction factor as (1−L d )+(WL m −WL m *L d ), wherein L d is the luminance value corresponding to said pixel and WL m , is an input parameter of the white point modulator;
a saturation modulator adapted to determine, for each pixel, the second saturation correction factor based on the saturation value from the luminance and saturation calculation unit; and
a hue modulator adapted to determine, for each pixel, the hue correction factor based on the saturation value from the luminance and saturation calculation unit.
3. The video processing device according to claim 2 , wherein the color gamut matrix generating unit is adapted to generate the color gamut matrix based upon measured characteristics of a display module.
4. The video processing device according to claim 3 , further comprising a memory adapted to store display module specific parameters.
5. The device of claim 2 , wherein the saturation modulator is adapted to generate, for each pixel, the second saturation correction factor as (1−S d )+(SS m −SS m *S d ), wherein S d is the saturation value corresponding to said pixel and SS m is an input parameter of the saturation modulator.
6. The device of claim 2 , wherein the hue modulator is adapted to generate, for each pixel, the hue correction factor as (1−S d )+(HS m −HS m *Sd), wherein S d is the saturation value corresponding to said pixel and HS m is an input parameter of the hue modulator.
7. The device of claim 1 , wherein the luminance and saturation calculation unit is adapted to calculate, for each pixel, the luminance value as the maximum of the squared amplitudes of the sub-pixels of said pixel.
8. The device of claim 1 , wherein the luminance and saturation calculation unit is adapted to calculate, for each pixel, the first saturation correction factor as (med−min)/(max+min), wherein max is the maximum of the squared amplitudes of the sub-pixels of said pixel, min is the minimum of the squared amplitudes of the sub-pixels of said pixel, and med is the median of the squared amplitudes of the sub-pixels of said pixel.
9. The device of claim 1 , wherein the saturation correction unit is adapted to output the saturation value for each pixel as s i *(1 31 c s /4), wherein s i and c s are the internal saturation and the first saturation correction factor, respectively, corresponding to said pixel.
10. A method of processing color image data, comprising the steps of:
squaring amplitudes of sub-pixels of pixels of an input video signal;
ranking the sub-pixels based on respective squared amplitude values of the sub-pixels;
calculating, for each pixel, a luminance value, an internal saturation, and a first saturation correction factor;
generating a saturation value for each pixel based on the internal saturation and the first saturation correction factor for said pixel;
transforming the luminance and saturation values of the pixels of the input video signal into a white-point correction factor, a second saturation correction factor, and a hue correction factor wherein the white-point correction factor is calculated for each pixel as (1−L d )+(WL m −WL m *L d ), wherein L d is the luminance value corresponding to said pixel and WL m is an input parameter;
generating a color gamut matrix in the perception domain based on the white-point correction factor, the second saturation correction factor, and the hue correction factor;
multiplying the pixels of the input video signal with the color gamut matrix; and
clipping the results of the color gamut mapping unit which are out of a predefined range.
11. The method of claim 10 , wherein transforming the luminance and saturation values of the pixels of the input video signal into the white-point correction factors, the second saturation correction factors, and the hue correction factors includes, for each pixel:
generating the corresponding white-point correction factor as (1−L d )+(WL m −WL m *L d ), wherein L d is the luminance value corresponding to said pixel and WL m is an input parameter; and
generating the corresponding second saturation correction factor and hue correction factor based on the corresponding saturation value.
12. The method of claim 11 , wherein the second saturation correction factor for each pixel is generated as (1−S d )+(SS m −SS m *S d ), wherein S d is the saturation value corresponding to said pixel and SS m is an input parameter.
13. The method of claim 11 , wherein the hue correction factor for each pixel is generated as (1−S d )+(HS m −HS m * Sd), wherein S d is the saturation value corresponding to said pixel and HS m is an input parameter.
14. The method of claim 10 , wherein the luminance value for each pixel is calculated as the maximum of the squared amplitudes of the sub-pixels of said pixel.
15. The method of claim 10 , wherein the first saturation correction factor for each pixel is calculated as (med−min)/(max+min), wherein max is the maximum of the squared amplitudes of the sub-pixels of said pixel, min is the minimum of the squared amplitudes of the sub-pixels of said pixel, and med is the median of the squared amplitudes of the sub-pixels of said pixel.
16. The method of claim 10 , wherein the saturation value for each pixel is generated as s i *(1−c s /4), wherein s i and c s are the internal saturation and the first saturation correction factor, respectively, corresponding to said pixel.