Gamut mapping method and apparatus
AssigneeSony Corporation
InventorsMasahiko Ito, Naoya Kato
Life of this patent
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Abstract
When an output color gamut is different from an input color gamut in a picture input/output system such as DTP, the color is corrected with a predetermined function for a difference in the lightness-directional dynamic range. A three-dimensional compression is made to compress the color of areas C and D to an area (A+B), and next a two-dimensional compression (or shrinkage) is made to compress the color of the area (B+C) to the area B, for example.
Claims17
A color mapping method of changing a color, when an output color gamut is different from an input color gamut, the input color gamut to the output color gamut, comprising:
- correcting the color using a predetermined function for a difference in the lightness-directional dynamic range, and
- correcting the color by a combination of a three-dimensional compression of lightness, chroma and hue and a two-dimensional shrinkage or expansion of the lightness and chroma, wherein correcting the color further includes:
- dividing the input gamut by four with a first straight line passing through a minimum value point L*min of the lightness L* in the output gamut and a second straight line passing through a maximum value point L*max of the lightness L* in the output gamut, these first and second straight lines intersecting each other at a point (C*th, L*_th) of the lightness value L*_th having a maximum chroma value C*_max of the output gamut in a two-dimensional plane of the lightness L* and chroma C* with the hue h kept constant, thereby defining an area A above the first straight line and below the second straight line, an input area B other than the area A and corresponding to the output color gamut, an input area C other than an area corresponding to the output color gamut, and an area D other than the output and input color gamuts;
- and
- leaving the color in the area A as it is and correcting the color by a combination of the three-dimensional compression and two-dimensional shrinkage or expansion.
A color mapping apparatus comprising:
- a color mapping means for changing, when an output color gamut is different from an input color gamut, a color in the input color gamut to one in the output color gamut by using a color mapping table, said color mapping table created by using a predetermined function for a difference in the lightness-directional dynamic range, and then combining a three-dimensional compression of lightness, chroma and hue and a two-dimensional shrinkage or expansion of the lightness and chroma, wherein said means includes means for dividing the input gamut by four with a first straight line passing through a minimum value point L*min of the lightness L* in the output gamut and a second straight line passing through a maximum value point L*max of the lightness L* in the output gamut, these first and second straight lines intersecting each other at a point (C*th, L*_th) of the lightness value L*_th having a maximum chroma value C*_max of the output gamut in a two-dimensional plane of the lightness L* and chroma C* with the hue kept constant, thereby defining an area A above the first straight line and below the second straight line, an input area B other than the area A and corresponding to the output color gamut, an input area C other than an area corresponding to the output color gamut, and an area D other than the output and input color gamuts.
Dependencies are inferred from the claim text.