Abstract: Gamut-mapping from a source device to a destination device is performed in a perceptually linear color space such as CIECAM02 by separating a source image into primary color components and processing each primary component separately by mapping a source cusp point with a destination cusp point. The mapped primary components are then summed and a resultant destination image is obtained. Alternatively, hue rotation is performed by determining a relative position of an input color between the nearest primary and the nearest secondary color in a source hue wheel. The determined relative position in the source hue wheel is used to find a corresponding location in a destination hue wheel so that a hue angle for the destination point can be obtained. In either process, the source and destination points are mapped using a cusp-to-cusp mapping process, and if the source point lies outside of the destination boundary after the cusp mapping, the point is mapped to the three-dimensional surface of the destination gamut.

Abstract: Techniques for use in gamut mapping processes are presented, including a method for mapping cusp points using hue wheels to obtain a source relative hue angle, and interpolating a lightness value at the source point hue. A maximum chroma value is determined at the source hue and the interpolated lightness, thus defining a source primary cusp point. A primary cusp point for a second color gamut is similarly obtained, and the source primary cusp point is mapped to the destination primary cusp point using a shear mapping technique. Another technique includes performing lightness compression by applying a chroma dependency factor and either a first or second factor, depending on a comparison of a lightness values of a destination point and a second point. Another technique involves performing chroma expansion by comparing chroma extents of source and destination points, and adjusting the chroma of the destination point based on the comparison.

Abstract: Gamut-mapping from a source device to a destination device is performed in a perceptually linear color space such as CIECAM02 by separating a source image into primary color components and processing each primary component separately by mapping a source primary hue leaf with a destination primary hue leaf. The mapped primary components are then summed and a resultant destination image is obtained. Alternatively, hue rotation is performed by determining a relative position of an input color between the nearest primary and the nearest secondary color in a source hue wheel. The determined relative position in the source hue wheel is used to find a corresponding location in a destination hue wheel so that the hue angle for obtaining the destination hue leaf can be determined. In both processes, the source and destination hue leafs are mapped using a cusp-to-cusp mapping with a shear mapping process being used to pull in the remaining colors.

Abstract: Tone mapping a high dynamic range (HDR) image is performed by obtaining a log-norm luminance component based on a normalized logarithm of the HDR image. The log-norm luminance component is flattened (tone-compressed) using incrementally-spaced adaptation levels, which are increasingly blurrier representations of the log-norm luminance component, weighted by a diminishing factor. Visual cues are restored by injecting a proportion of values of the log-norm luminance component, applying histogram tail clipping, and applying a sigmoid curve mapping, to create a restored luminance component. A tone-compressed image is obtained by mapping luminance of the HDR image using the restored luminance component and adjusting saturation of the mapped HDR image.

Abstract: A table representing a color gamut for a device for use in a color management system where colors are represented in a color appearance space comprises data representing a collection of hue slices through a boundary surface of the color gamut. The collection of hue slices comprises entries for vertex point hue slices obtained at each vertex point on the boundary surface of the color gamut, and entries obtained for additional hue slices between adjoining vertex point hue slices, where a number of the additional hue slices is determined such that there is no more than a specified angular difference between each hue slice. Each hue slice is represented by a hue value and a collection of hue slice points each containing a lightness value and a chroma value.

Abstract: In converting a color in a source gamut to a color in a destination gamut, selection of a conversion technique is determined for the source color based on the hue aspect of the source color, a maximum chroma of the destination gamut associated with the source color's hue aspect, and the lightness value of the source color relative to a lightness value associated with the maximum chroma. In converting a set of colors such as in a digital color image, selection of a conversion technique is performed for each color in the color image, independent of the color aspects of, and/or the conversion technique selected for, neighboring colors.