A method and apparatus of encoding and decoding a color picture

A method for encoding a color picture having color components comprising obtaining a luminance component (L) and two final chrominance components (C1, C2) from the color picture to be encoded, obtaining a final luminance component (L″) and two final chrominance components (C1″, C2″), and encoding said final luminance component (L″) and said at least one final chrominance component,

• characterized in that the method further comprises:
• determining a first factor (β−1(L(i)) based on the value of each pixel (i) of the luminance component (L);
• obtaining the two final chrominance components (C1″, C2″) by scaling the two chrominance components (C1, C2) by the first factor;
• and—obtaining the final luminance component (L″) by linearly combining together the luminance component (L) and the two final chrominance components (C1″, C2″) as follows:
• L″=L−mC″1−nC″2
• where L is the luminance component, L″ is the final luminance component, C″1 and C″2 are the two final chrominance components, m and n are none null coefficients.

A Method for decoding a color picture from a bitstream, comprising obtaining a luminance component (L″) and two chrominance components (C1″, C2″) from the bitstream;

• obtaining two final chrominance components (C1, C2) from the two chrominance components (C1″, C2″);
• and
• obtaining the color picture to be decoded from the final luminance component (L) and the two final chrominance components,
• characterized in that obtaining the two final chrominance components comprises:
• obtaining a first factor (β−1(L(i)) from the value of each pixel (i) of the final luminance component (L);
• obtaining the two final chrominance component (C1, C2) by multiplying the two chrominance component (C1″, C2″) by the first factor;
• obtaining the final luminance component (L) by linearly combining together the luminance component (L″) and the two chrominance components as follows:
• L=L″+mC″1+nC″2
• where L is the final luminance component, L″ is the luminance component, C″1 and C″2 are the two chrominance components, m and n are none null coefficients.

A device for encoding a color picture having color components comprising a processor configured to obtain a luminance component (L) and two final chrominance components (C1, C2) from the color picture to be encoded, to obtain a final luminance component (L″) and two final chrominance components (C1″, C2″), and to encode said final luminance component (L″) and said at least one final chrominance component, wherein the processor is further configured to:

• determine a first factor (β−1(L(i)) based on the value of each pixel (i) of the luminance component (L);
• obtain the two final chrominance components (C1″, C2″) by scaling the two chrominance components by the first factor;
• and
• obtain the final luminance component (L″) by linearly combining together the luminance component (L) and the two final chrominance components (C1″, C2″) as follows:
• L″=L−mC″1−nC″2
• where L is the luminance component, L″ is the final luminance component, C″1 and C″2 are the two final chrominance components, m and n are none null coefficients.

A device for decoding a color picture from a bitstream, comprising a processor configured to:

• obtain a luminance component (L″) and two chrominance component (C1″, C2″) from the bitstream;
• obtain two final chrominance components (C1, C2) from the two chrominance components;
• and
• obtain the color picture to be decoded from the two final chrominance components (C1″, C2″),
• wherein the processor is further configured to obtain the two final chrominance components by:
• obtaining a first factor β−1(L(i)) from the value of each pixel (i) of the final luminance component (L);
• obtaining the two final chrominance components (C1, C2) by multiplying the two chrominance components (C1″, C2″) by the first factor;
• obtaining the final luminance component (L) by linearly combining together the luminance component (L″) and the two chrominance components (C1″, C2″) as follows:
• L=L″+mC″1+nC″2
• where L is the final luminance component, L″ is the luminance component, C″1 and C″2 are the two chrominance components, m and n are none null coefficients.