Method and device for color gamut mapping

A method comprising gamut mapping from a wide color gamut towards a standard color gamut, the gamut mapping comprising:

• for each key color of a group of three primary colors and three secondary colors in the wide color gamut, obtaining a preservation ratio and a hue alignment angle for the key color, wherein the preservation ratio as applied to a saturation of the key color in a chroma plane defines a preserved key color that identifies a preserved area, the hue alignment angle corresponding to the angle formed between the key color of the wide color gamut mapped into the standard color gamut and key color in the wide color gamut with respect to an origin in the chroma plane;
• and
• performing a hue mapping of a current color from the wide color gamut towards the standard color gamut comprising:
• determining a primary color and an adjacent secondary color in the wide color gamut in a sector in which the current color belongs;
• determining a rotated primary color by projecting the primary color on a rotated primary color hue line being a hue line through the primary color rotated by the hue alignment angle of the primary color, and determining a rotated secondary color by projecting the adjacent secondary color on a rotated secondary color hue line being a hue line through the adjacent secondary color rotated by the hue alignment angle of the adjacent secondary color;
• determining a preserved primary color using the preservation ratio of the primary color and determining a preserved adjacent secondary color using the preservation ratio of the adjacent secondary color;
• and
• when the current color is out of the preserved area, determining the hue mapped current color comprising:
• determining an anchor at an intersection of a line through the rotated primary color and the preserved primary color and a line through the rotated adjacent secondary color and the preserved adjacent secondary color;
• determining a preserved current color at an intersection of a hue line through the current color and the origin in the chroma plane and a preservation line through the preserved primary color and the preserved secondary color;
• obtaining the hue mapped current color by projecting the current color on a hue line defined by the preserved current color and the anchor.

A device comprising one or more processors and at least one memory having stored instructions operative, when executed by the one or more processors, to cause the device to perform gamut mapping from a wide color gamut towards a standard color gamut, the gamut mapping comprising:

• for each key color of a group of three primary colors and three secondary colors in the wide color gamut, obtaining a preservation ratio and a hue alignment angle for the key color, wherein the preservation ratio as applied to a saturation of the key color in a chroma plane defines a preserved key color that identifies a preserved area, the hue alignment angle corresponding to the angle formed between the key color of the wide color gamut mapped into the standard color gamut and key color in the wide color gamut with respect to an origin in the chroma plane;
• and
• performing a hue mapping of a current color from the wide color gamut towards the standard color gamut comprising:
• determining a primary color and an adjacent secondary color in the wide color gamut in a sector in which the current color belongs;
• determining a rotated primary color by projecting the primary color on a rotated primary color hue line being a hue line through the primary color rotated by the hue alignment angle of the primary color, and determining a rotated secondary color by projecting the adjacent secondary color on a rotated secondary color hue line being a hue line through the adjacent secondary color rotated by the hue alignment angle of the adjacent secondary color;
• determining a preserved primary color using the preservation ratio of the primary color and determining a preserved adjacent secondary color using the preservation ratio of the adjacent secondary color;
• and
• when the current color is out of the preserved area, determining the hue mapped current color comprising:
• determining an anchor at an intersection of a line through the rotated primary color and the preserved primary color and a line through the rotated adjacent secondary color and the preserved adjacent secondary color;
• determining a preserved current color at an intersection of a hue line through the current color and the origin in the chroma plane and a preservation line through the preserved primary color and the preserved secondary color;
• obtaining the hue mapped current color by projecting the current color on a hue line defined by the preserved current color and the anchor.

A method comprising an inverse gamut mapping from a standard color gamut towards a wide color gamut, the inverse gamut mapping comprising:

• for each key color of a group of three primary colors and three secondary colors in the wide color gamut, obtaining a preservation ratio and a hue alignment angle for the key color, wherein the preservation ratio as applied to a saturation of the key color in a chroma plane defines a preserved key color that identifies a preserved area, the hue alignment angle corresponding to the angle formed between the key color in the wide color gamut mapped into the standard color gamut and key color in the wide color gamut with respect to an origin in the chroma plane;
• and
• performing a hue remapping of a current color from the standard color gamut towards the wide color gamut comprising:
• determining a primary color and an adjacent secondary color in the wide color gamut in a sector in which the current color belongs;
• determining a rotated primary color by projecting the primary color on a rotated primary color hue line being a hue line through the primary color rotated by the hue alignment angle of the primary color and determining a rotated secondary color by projecting the adjacent secondary color on a rotated secondary color hue line being a hue line through the adjacent secondary color rotated by the hue alignment angle of the adjacent secondary color;
• determining a preserved primary color using the preservation ratio of the primary color and determining a preserved adjacent secondary color using the preservation ratio of the adjacent secondary color;
• and
• when the current color is out of the preserved area, determining the hue remapped current color comprising:
• determining an anchor at an intersection of a line through the rotated primary color and the preserved primary color and a line through the rotated adjacent secondary color and the preserved adjacent secondary color;
• determining a preserved current color at an intersection of a line through the current color and the anchor in the chroma plane and a preservation line through the preserved primary color and the preserved secondary color;
• obtaining the hue remapped current color by projecting the current color on a hue line defined by the preserved current color and the origin.

A device comprising one or more processors and at least one memory having stored instructions operative, when executed by the one or more processors, to cause the device to perform an inverse gamut mapping from a standard color gamut towards a wide color gamut, the inverse gamut mapping comprising:

• for each key color of a group of three primary colors and three secondary colors in the wide color gamut, obtaining a preservation ratio and a hue alignment angle for the key color, wherein the preservation ratio as applied to a saturation of the key color in a chroma plane defines a preserved key color that identifies a preserved area, the hue alignment angle corresponding to the angle formed between the key color in the wide color gamut mapped into the standard color gamut and key color in the wide color gamut with respect to an origin in the chroma plane;
• and
• performing a hue remapping of a current color from the standard color gamut towards the wide color gamut comprising:
• determining a primary color and an adjacent secondary color in the wide color gamut in a sector in which the current color belongs;
• determining a rotated primary color by projecting the primary color on a rotated primary color hue line being a hue line through the primary color rotated by the hue alignment angle of the primary color and determining a rotated secondary color by projecting the adjacent secondary color on a rotated secondary color hue line being a hue line through the adjacent secondary color rotated by the hue alignment angle of the adjacent secondary color;
• determining a preserved primary color using the preservation ratio of the primary color and determining a preserved adjacent secondary color using the preservation ratio of the adjacent secondary color;
• and
• when the current color is out of the preserved area, determining the hue remapped current color comprising:
• determining an anchor at an intersection of a line through the rotated primary color and the preserved primary color and a line through the rotated adjacent secondary color and the preserved adjacent secondary color;
• determining a preserved current color at an intersection of a line through the current color and the anchor in the chroma plane and a preservation line through the preserved primary color and the preserved secondary color;
• obtaining the hue remapped current color by projecting the current color on a hue line defined by the preserved current color and the origin.