Abstract: Color characterization of a high dynamic range (HDR) image capture device is provided. Color checker image data of a color checker at multiple exposures is obtained. Color values for neutral patches and exposure values are extracted. A colorimetrically accurate response curve is determined based on the neutral patch color values and the exposure values. An optimized transformation associated with the device is derived through gamma curve compensation based on the neutral patch data and comparison of color values of the compensated image with known color values of the color checker. A calorimetrically accurate HDR image is generated from scene image data of a scene captured by the device at multiple exposures through extraction of exposure data, modification of color values based on the colorimetrically accurate response curve and the exposure data, averaging the modified color values, and transformation of the averaged color values based on the optimized transformation.

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: White balance normalization of a high dynamic range image is performed by identifying a first image adaptation point for a relatively lighter portion of the image and a second image adaptation point for a relatively darker portion of the image. A first white point adjustment for the lighter portion of the image is performed using the first image adaptation point and a second white point adjustment for the darker portion of the image is performed using the second image adaptation point. Thus, multiple illumination sources can be taken into account in rendering a high dynamic range image, providing a more visually appealing rendered image.

Abstract: Mapping color image data from a source color gamut to a destination color gamut, wherein the mapping includes identifying source color boundary regions in the source color gamut based on descriptor data provided in a source color descriptor data structure, and determining a position of each identified source color boundary region, identifying destination color boundary regions in the destination color gamut based on descriptor data provided in a destination color descriptor data structure, and determining a position of each identified destination color boundary region, and mapping the color image data from the identified source color boundary regions to the identified destination color boundary regions based on a correspondence between the determined positions of the identified source color boundary regions and the determined positions of the identified destination color boundary regions.

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.

Abstract: A color descriptor data structure corresponding to a color device, the color descriptor data structure including a reference color data set corresponding to a reference boundary descriptor representing reference colors of the color device based on measured colors from a reference color target, a plausible color data set corresponding to a plausible boundary descriptor representing plausible colors of the color device which are observable, which encompass at least the reference colors of the reference boundary descriptor, and which include a whitest-white color and a blackest-black color, and a neutral color data set corresponding to neutral colors of the color device, the neutral colors extending in range from the whitest-white color to the blackest-black color.

Abstract: Color characterization of a high dynamic range (HDR) image capture device is provided. Color checker image data of a color checker at multiple exposures is obtained. Color values for neutral patches and exposure values are extracted. A colorimetrically accurate response curve is determined based on the neutral patch color values and the exposure values. An optimized transformation associated with the device is derived through gamma curve compensation based on the neutral patch data and comparison of color values of the compensated image with known color values of the color checker. A calorimetrically accurate HDR image is generated from scene image data of a scene captured by the device at multiple exposures through extraction of exposure data, modification of color values based on the colorimetrically accurate response curve and the exposure data, averaging the modified color values, and transformation of the averaged color values based on the optimized transformation.

Abstract: The present invention relates to a color management method for the conversion of internal color appearance space color values to CMYK device values, by interpolating CMY values from a plurality of CMY to color appearance space lookup tables, wherein each CMY table is associated with a specific value of K. A target internal color value is received and the relative purity of that color is calculated in the CMY space. Next, a black generation value is calculated using the relative purity of the target color. Finally, one of the plurality of CMY lookup tables is selected based on the black generation value, and a CMYK value is provided based on an interpolation from the selected lookup table. In this way, the present invention is able to control the output K value in a color appearance space to CMYK conversion. Accordingly, colors across a wide relative purity range, including natural images, can be reproduced with better accuracy and higher quality.

Abstract: White balance normalization of a high dynamic range image is performed by identifying a first image adaptation point for a relatively lighter portion of the image and a second image adaptation point for a relatively darker portion of the image. A first white point adjustment for the lighter portion of the image is performed using the first image adaptation point and a second white point adjustment for the darker portion of the image is performed using the second image adaptation point. Thus, multiple illumination sources can be taken into account in rendering a high dynamic range image, providing a more visually appealing rendered image.

Abstract: The present invention relates to a color management method for the conversion of internal color appearance space color values to CMYK device values, by interpolating CMY values from a plurality of CMY to color appearance space lookup tables, wherein each CMY table is associated with a specific value of K. A target internal color value is received and the relative purity of that color is calculated in the CMY space. Next, a black generation value is calculated using the relative purity of the target color. Finally, one of the plurality of CMY lookup tables is selected based on the black generation value, and a CMYK value is provided based on an interpolation from the selected lookup table. In this way, the present invention is able to control the output K value in a color appearance space to CMYK conversion. Accordingly, colors across a wide relative purity range, including natural images, can be reproduced with better accuracy and higher quality.

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: 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.

Abstract: Mapping color image data from a source color gamut to a destination color gamut, wherein the mapping includes identifying source color boundary regions in the source color gamut based on descriptor data provided in a source color descriptor data structure, and determining a position of each identified source color boundary region, identifying destination color boundary regions in the destination color gamut based on descriptor data provided in a destination color descriptor data structure, and determining a position of each identified destination color boundary region, and mapping the color image data from the identified source color boundary regions to the identified destination color boundary regions based on a correspondence between the determined positions of the identified source color boundary regions and the determined positions of the identified destination color boundary regions.

Abstract: A color descriptor data structure corresponding to a color device, the color descriptor data structure including a reference color data set corresponding to a reference boundary descriptor representing reference colors of the color device based on measured colors from a reference color target, a plausible color data set corresponding to a plausible boundary descriptor representing plausible colors of the color device which are observable, which encompass at least the reference colors of the reference boundary descriptor, and which include a whitest-white color and a blackest-black color, and a neutral color data set corresponding to neutral colors of the color device, the neutral colors extending in range from the whitest-white color to the blackest-black color.