The present invention generally relates to a method and arrangement for estimating said at least one cross-channel color mapping model from a set of tuples of corresponding colors relative to at least two images. The method is characterized in that it uses a processor for selecting at least one intermediate tuple of corresponding colors from the set of tuples of corresponding colors by using at least one channel-wise color mapping model, and for estimating the at least one cross-channel color mapping model from the at least one intermediate selected tuple of corresponding colors.

A color conversion method includes: a first acquisition step of acquiring a first color conversion table which defines mapping from a first color space to a second color space, and a second color conversion table which defines mapping from the second color space to a third color space; a second acquisition step of acquiring a color in the second color space to be subjected to color conversion; a computation step of computing an element group and a weight of each element included in the element group; a determination step of determining whether or not the element group in the second color conversion table; and a processing step of performing either first processing of performing inverse conversion and computing the color in the third color space, or second processing of performing an interpolation computation and computing the color in the third color space.

Methods and apparatus for rendering and displaying high dynamic range (HDR) digital image content according to a perceptual model. A model of viewer perceptual range may be determined according to the perceptual model based on inputs including ambient lighting conditions, display panel characteristics (e.g., light leakage and reflected ambient light), and/or display panel settings. The system may determine, according to the model of viewer perceptual range, a brightness level that defines a lower portion and an upper portion of a display space of the display panel, and a maximum rendering value M. Digital image content may be rendered according to the maximum rendering value M to generate HDR content in a dynamic range of (0.0-M). The rendered HDR content may then be mapped into the display space of the display panel according to the brightness level.

A method of performing gamut mapping on an input image for an image output device includes receiving the input image to analyze a color distribution of the input image; determining a protect range corresponding to a first percentage of color codes of the input image and a compression range corresponding to a second percentage of the color codes of the input image based on the color distribution of the input image; and moving at least one of the color codes of the input image outside the protect range of the color codes to the compression range by a compression algorithm to perform gamut mapping on the input image.

Techniques for interactively determining/visualizing the color content of a source image and how the corresponding image data is mapped to device colors are described herein. For example, the color content of a digital image can be converted between different color spaces to identify gamut limitations of an output device (e.g., a printing assembly), discover color(s) that cannot be accurately reproduced, etc. Color space conversions enable the transformation of the color content of the digital image from device-specific colorants to a device-independent representation (and vice versa). In some embodiments, these transformations are facilitated using lookup tables that are implemented in graphical processing unit-resident memory.

According to exemplary methods, a processor of a printing device determines color values out of a first colorant combination using marking materials for standard colorants and marking materials for one or more extended gamut colors. The extended gamut color has colorants other than the standard colorants. Responsive to the first colorant combination including color values for each of a pair of two complementary colors, the processor calculates a second colorant combination that produces the same human-perceivable color as the first colorant combination. The second colorant combination includes only one color of the pair of two complementary colors. The printing device produces output using the second colorant combination for the standard colorants and the extended gamut color.

A data segmenter is configured to determine indices using numbers of most significant bits (MSBs) of fractional values of floating-point representations of component values of an input color that are selected based on exponent values of the floating-point representations. The component values are defined according to a source gamut. The data segmenter is also configured to determine offsets associated with the indices using subsets of the fractional values. An interpolator configured to map the input color to an output color defined according to a destination gamut based on a location in a three-dimensional (3-D) look up table (LUT) indicated by the indices and offsets.

An image processing method includes obtaining color information of each of a plurality of pixels included in an input image signal; determining whether a color value of each of the plurality of pixels corresponds to a gamut boundary of the input image signal based on the obtained color information; determining a gain value for allowing the color value of at least one of the plurality of pixels to correspond to the gamut boundary, based on a result of the determining; and converting the color value of the at least one pixel based on the determined gain value.

The present disclosure generally relates a method and device for processing color image data. The method comprises a color gamut mapping in the course of which a color image data (CID), represented by a first 2D point (A) belonging to a representation of the original color gamut in a chromaticity diagram, is mapped to a mapped color image data (MCID) of a target color gamut (TCG), the mapped color image data of the target color gamut (TCG) being represented by a second 2D point (B) belonging to a representation of the target color gamut (TCG) in the chromaticity diagram, wherein the color gamut mapping comprises: obtaining (100) a representation of a preserved color gamut (PCG) in the chromaticity diagram by applying an homothety either to the original color gamut or to the target color gamut; checking (110) if said first 2D point is located outside the representation of the preserved color gamut (PCG); and when said first 2D point is located outside the representation of the preserved color gamut (PCG), moving (300) said first 2D point so that it belongs to the representation of the target color gamut (TCG), the second 2D point being then equal to the moved first 2D point. The disclosure relates also to a method and device for encoding/decoding color image data.

A gamut size metric is used in all phases of color image processing (e.g., capture, transmission, and display). In general, the gamut size metric is a single-valued metric that changes as image content changes. More particularly, a gamut boundary histogram is determined and used to estimate a gamut size metric. A gamut size metric identifies a minimum size gamut needed to encompass each pixel in an image, where the gamut size is limited at one end by a first device independent gamut (S.sub.1), and at another end by a second device independent color space (S.sub.2), where S.sub.1 is wholly enclosed within S.sub.2. The gamut size metric may be based on strict pixel color value differences. In other embodiments the gamut size metric may take into effect perceptual color differences and significance.