Perceptually optimised color calibration method and system
Methods, devices, controllers and systems for color calibration of displays, non-volatile (non-transient) memory, controllers, display devices or display systems including a color calibration transform, operation of such controllers, display devices or systems and software for color calibration of a display are described are described that make use of a color transform having a distribution of color points across a full display gamut (hence optionally preserving full contrast and color saturation in the calibrated display) in an at least substantially perceptually uniform manner suitable for use as a color display calibration adapted for medical applications. A perceptually uniform spread of color points can be in terms of a distance metric such as deltaE2000 for color or JND for gray.
1. A display device having a native gamut defined in a first color space, the display device comprising:
a non-volatile memory storing a calibration transform configured to linearize a color space, wherein:
the calibration transform has a set of calibrated color points derived from color points of the native gamut; and
the set of calibrated color points has improved perceptional linearity compared with the native gamut while preserving the color gamut: and
a processor configured to:
receive an image defined In a first colors space to be displayed on the display device;
receive the calibration transform from the memory:
apply the received calibration transform to the received image to generate a calibrated image, such that:
a color space of the calibrated image is linearized:
the color space of the calibrated image has improved perceptional linearity compared to the native gamut; and
the color gamut of the received image is preserved in the calibrated image; and
cause the calibrated image to be displayed.
2. The display device of claim 1 , wherein the calibration transform is stored in a non-volatile 3D LUT (lookup table) memory.
3. The display device of claim 2 , further comprising a graphical user interface for inputting a color point of the native gamut to the non-volatile 3D LUT memory and for outputting a calibrated color point in accordance with the color transform.
4. The display device of claim 2 , wherein the non-volatile 3D LUT memory stores color points equidistant in three dimensions.
5. The display device of claim 4 , wherein the color points stored in the non-volatile 3D LUT memory are spaced by a color distance metric.
6. The display device of claim 5 , wherein the color points stored in the non-volatile 3D LUT memory are spaced by a first distance metric in a first part of a color space, and a second distance metric in another part of the color space.
7. The display device of claim 6 , wherein a second part of the color space primarily contains a neutral grey part of the color space and where the first part of the color space primarily excludes the neutral grey part of the color space.
8. The display device of claim 6 , further comprising a border area between the first part of the color space and a second part of the color space, the border area being smoothed with reduced discontinuities.
9. The display device of claim 5 , wherein the color points are equidistant in terms of the color distance metric.
10. The display device of claim 5 , wherein gray points in the color space are equidistant in terms of a second distance metric.
11. The display device of claim 2 , wherein the non-volatile 3D LUT memory is in a display controller.
12. The display device of claim 2 , wherein the non-volatile 3D LUT memory is associated with a GPU.
13. The display device of claim 2 , wherein the non-volatile 3D LUT memory is in a display controller.
14. The display device of claim 2 , wherein the non-volatile 3D LUT memory is in a pixel shader.
15. The display device of claim 1 , wherein the calibration transform conforms to a DICOM (Digital Imaging and Communications in Medicine) standard.