Gamut map model with improved gradation fidelity at low chroma values
An improved gamut map model (GMM) useful in conjunction with Windows Color System (WCS). The method uses the WCS Minimum Color Difference (MinCD) GMM to handle gamut mapping for the Saturation rendering intent at low input chroma values. For input values to the gamut map model profile (GMMP), if the chroma value C falls within a predetermined chroma value range, the MinCD GMM will be applied, otherwise the Hue Mapping GMM is applied. The predetermined chroma value range can be determined by experimentation. The range is 0≦C≦10 in a preferred embodiment. This method will improve the gradation fidelity of the rendered images and reduce or prevent major hue shifts at low chroma values. The method may be implemented as a plug-in utility for a computer.
1. A method for rendering an image on a device, the image being defined by a plurality of input points each having input color values, the method comprising:
for each input point:
calculating a lightness value, a chroma value, and a hue value from the input color values;
if the calculated chroma value falls within a predetermined range, using Minimum Color Difference as a gamut map model in a Gamut Map Model Profile to generate output color values; and
if the calculated chroma value falls outside of the predetermined range, using Hue Mapping as the gamut map model in the Gamut Map Model Profile to generate output color values; and
rendering the image using the output color values.
2. The method of claim 1 , wherein the predetermined range is from 0 to 10 inclusive.
3. A computer usable non-transitory medium having a computer readable program code embedded therein for controlling a data processing apparatus, the computer readable program code configured to cause the data processing apparatus to execute a process for mapping input color values to output color values, the process comprising:
for each input point:
calculating a lightness value, a chroma value, and a hue value from the input color values;
if the calculated chroma value falls within a predetermined range, using Minimum Color Difference as a gamut map model in a Gamut Map Model Profile to generate output color values; and
if the calculated chroma value falls outside of the predetermined range, using Hue Mapping as the gamut map model in the Gamut Map Model Profile to generate output color values.
4. The computer usable non-transitory medium of claim 3 , wherein the predetermined range is from 0 to 10 inclusive.