Observer metameric failure reduction method

1. A method for color correcting a color image to account for color vision characteristics associated with a set of target observers in preparation for displaying the color image on a color display device having a plurality of device color primaries, at least one of the device color primaries being a narrow-band primary, comprising:

receiving an input color image in an input color space, the input color image being adapted for display on a reference color display device having a plurality of input color primaries having associated input color primary spectra;

using a data processing system to apply a metamerism correction transform to the input color image to determine an output color image in an output color space appropriate for display on the color display device, the output color image having a plurality of output color channels, each of the output color channels being associated with one of the device color primaries, wherein the metamerism correction transform modifies colorimetry associated with the input colors to provide output color values such that an average observer metameric failure is reduced for a distribution of target observers that includes a plurality of target observers who are simultaneously viewing the color display device, the plurality of target observers having disparate color vision characteristics; and

storing the output color image in a processor accessible memory;

wherein the metamerism correction transform is determined by:

defining a set of input color values in the input color space;

determining a corresponding set of output color values in the output color space such that CIE colorimetry determined for the input color values displayed using the input color primaries substantially matches CIE colorimetry determined for the corresponding output color values displayed using the device color primaries;

for each input color value determining a distribution of perceived color difference corresponding to the distribution of target observers, wherein the perceived color difference for a particular target observer represents a difference between a color appearance of the input color value displayed using the input color primaries and a color appearance of the corresponding output color value displayed using the device color primaries;

determining a set of corrected output color values corresponding to the set of input color values, wherein each corrected output color value is determined according to the distribution of perceived color differences; and

forming the metamerism correction transform responsive to the set of input color values and the corresponding set of corrected output color values.

2. The method of claim 1 wherein the distribution of perceived color differences for a particular input color value is determined by:

receiving observer-specific color matching functions associated with the plurality of target observers in the distribution of target observers;

determining an input color spectrum produced when the particular input color value is displayed using the input color primaries;

determining a narrow-band color spectrum produced using the device color primaries that provides substantially identical CIE colorimetry as the input color spectrum, wherein the CIE colorimetry is determined using a set of CIE standard observer color matching functions;

for each target observer using the corresponding observer-specific color matching functions to determine user-specific input colorimetry corresponding to the input color spectrum and to determine user-specific narrow-band colorimetry corresponding to the narrow-band color spectrum; and

for each target observer determining the perceived color difference responsive to the user-specific input colorimetry and the user-specific narrow-band colorimetry.

3. The method of claim 1 wherein the corrected output color values are determined by computing a central tendency for the distribution of matching output color values, the central tendency being an average, a weighted average, a geometric mean or a median.

4. The method of claim 1 wherein the colorimetry modifications provided by the metamerism correction transform vary for different input color values.

5. The method of claim 1 wherein the input color space is portioned into an inner color gamut zone, an extended color gamut zone, and a transition zone containing the colors between the inner color gamut zone and the extended color gamut zone, and wherein the color metamerism correction transform applies color shifts determined in responsive to the set of input color values and the corresponding set of corrected output color values within the inner color gamut zone, and applies no color shifts in the extended color gamut zone, and wherein the color metamerism correction transform provides a smooth transition across the transition zone between the color shifts applied in the inner color gamut zone and the extended color gamut zone.

6. The method of claim 5 wherein a width of the transition zone varies responsive to a size of the color shifts applied in a corresponding portion of the inner color gamut zone.

7. The method of claim 5 wherein the color shifts applied for input color values in the transition zone are modified to maintain continuity of local image content.

8. The method of claim 1 wherein the metamerism correction transform is a parametric function having a plurality of parameters, and wherein the parameters are determined by applying a fitting process responsive to the set of input color values and the corresponding set of output color values.

9. The method of claim 1 wherein the metamerism correction transform is a multi-dimensional look-up table that stores output color values corresponding to a lattice of input color values, the stored output color values providing reduced average observer metameric failure for the distribution of target observers.

10. The method of claim 9 wherein the output color values stored in the multi-dimensional look-up table are determined by fitting a smooth function to the set of input color values and the corresponding set of output color values.

11. The method of claim 1 wherein a standard color transform is used to transform the input color values in the input color image to standard output color values, the standard color transform being adapted to determine output color values that produce output CIE colorimetry that substantially matches input CIE colorimetry determined for the input color values, the CIE output colorimetry being determined using CIE standard observer color matching functions for an output color spectrum produced when the output color value is displayed using the device color primaries and the input CIE colorimetry being determined using the CIE standard observer color matching functions for an input color spectrum produced when the input color value is displayed using the device color primaries; and wherein the metamerism correction transform transforms the standard output color values to corresponding corrected output color values that account for the color vision characteristics associated with the distribution of target observers.

12. The method of claim 1 wherein the color vision characteristics associated with the distribution of target observers are characterized by a corresponding set of observer-specific color matching functions.

13. The method of claim 1 wherein different color metamerism correction transforms are selected for use responsive to demographics of observers viewing the color display device, or responsive to a state of adaptation for observers viewing the color display device.

14. The method of claim 1 wherein the distribution of target observers is a plurality of target observers determined to be representative of a population of target observers.

15. The method of claim 1 wherein at least one of the device color primaries is provided by a laser light source or an LED light source.

16. The method of claim 1 wherein the narrow-band primaries have a spectral bandwidth of no more than 30 nm.

17. The method of claim 1 wherein the input color primaries are wide-band primaries having a spectral bandwidth of at least 45 nm.

18. The method of claim 1 further including displaying the output color image on the color display device, and wherein the color values displayed on the color display device are temporally dithered between a series of dithering colors having colors that surround the output color values.

19. The method of claim 4 wherein the colorimetry modifications that vary for different input color values provide compensating color shifts that correct for color-dependent characteristics in the distribution perceived color differences corresponding to the distribution of target observers.