Method for radiometric compensated display, corresponding system, apparatus and computer program product

Patent metadata

Field	Value
Publication number	US-10152944-B2
Application number	US-201514870131-A
Country	US
Kind code	B2
Filing date	Sep 30, 2015
Priority date	Dec 24, 2014
Publication date	Dec 11, 2018
Grant date	Dec 11, 2018

Abstract

Color signals to be displayed on a colored display surface and having a first gamut in a color space, are subjected to radiometric compensation. An embodiment includes displaying on the colored surface a set of control points of a known color, acquiring via a camera the control points as displayed on the colored surface and evaluating at least one second color gamut of the control points displayed on the colored surface. The second color gamut(s) is/are misaligned with respect to the first color gamut due to the display surface being a colored surface. The method may also include evaluating as an intersection gamut, the misalignment of the second color gamut(s) with respect to the first color gamut, calculating the color transformation operator(s) as a function of the misalignment evaluated, and applying the color transformation operator(s) to the color signals for display on the colored display surface.

First claim

That which is claimed:

1. A radiometric compensation method for displaying, on a colored display surface, color signals having a first color gamut in a color space, the method comprising:
displaying on the colored display surface a set of control points of a known color, wherein the colored display surface is a non-uniformly colored display surface and includes areas of different colors;
acquiring the control points as displayed on the colored display surface, wherein the control points displayed on the colored display surface as acquired have a plurality of second color gamuts which are misaligned with respect to the first color gamut due to the colored display surface being a non-uniformly colored display surface;
evaluating misalignments of the plurality of second color gamuts with respect to the first color gamut for areas including clustered pixels of the colored display surface, the clustering being based on color classes;
calculating a plurality of respective color transformation operators as a function of the misalignments; and
applying the respective color transformation operators to the areas of different colors of the non-uniformly colored display surface for display on the non-uniformly colored display surface.

2. The method of claim 1 , comprising displaying on the colored display surface the color signals to which the respective color transformation operators have been applied.

3. The method of claim 1 , further comprising:
evaluating the misalignments of the plurality of second color gamuts with respect to the first color gamut as an intersection gamut therebetween; and
calculating the respective color transformation operators as at least one mapping operator mapping the first color gamut to the intersection gamut.

4. The method of claim 3 , further comprising performing a boosting action of the color signals, by allowing a certain amount of clipping at the intersection gamut.

5. The method of claim 1 , further comprising:
generating a set of lines joining the control points to a middle grey color;
sampling each line in the set from the middle grey color by finding a point common to the first color gamut and the plurality of second color gamuts displayable on the colored display surface; and
calculating the respective color transformation operators as a transformation matrix from the control points to the common points found.

6. The method of claim 1 , further comprising:
converting the color signals for display on the colored display surface to a device-independent XYZ color space;
subjecting the color signals converted to the device-independent color space to radiometric compensation as a function of the respective color transformation operators; and
converting the color signals subjected to radiometric compensation to conversion from the device-independent color space to a display color space for display on the color display surface.

7. An electronic device comprising:
a processor and a memory coupled thereto and configured to perform radiometric compensation for displaying on a colored display surface color signals having a first color gamut in a color space by at least:
displaying on the colored display surface a set of control points of a known color,
acquiring the control points as displayed on the colored display surface, wherein the control points displayed on the colored display surface as acquired have at least one second color gamut which is misaligned with respect to the first color gamut due to the colored display surface being a colored surface,
evaluating the misalignment of the at least one second color gamut with respect to the first color gamut, wherein evaluating the misalignment comprises:
generating a set of lines joining the control points to a middle grey color; and
sampling each line in the set from the middle grey color by finding a point common to the first color gamut and the at least one second color gamut displayable on the colored display surface;

calculating at least one color transformation operator as a transformation matrix from the control points to the common points found, and
applying the at least one color transformation operator to the color signals for display on the colored display surface.

8. The electronic device of claim 7 , wherein the processor and memory are configured to display on the colored display surface the color signals to which the color transformation operator has been applied.

9. The electronic device of claim 7 , wherein the colored display surface is of non-uniform color and includes areas of different colors and the control points displayed on the colored display surface as acquired have a plurality of second color gamuts which are misaligned with respect to the first color gamut; and wherein the processor and memory are configured to evaluate misalignments of the second color gamuts of the plurality with respect to the first color gamut, calculate as a function of the misalignments a plurality of respective transformation operators, and apply the respective color transformation operators to the areas of different colors of the non-uniformly colored display surface.

10. The electronic device of claim 7 , wherein the processor and memory are configured to:
evaluate the misalignment of the at least one second color gamut with respect to the first color gamut as an intersection gamut therebetween; and
calculate the at least one color transformation operator as at least one mapping operator mapping the first color gamut to the intersection gamut.

11. The electronic device of claim 7 , wherein the processor and memory are configured to:
convert the color signals for display on the colored display surface to a device-independent XYZ color space;
subject the color signals converted to the device-independent color space to radiometric compensation as a function of the at least one color transformation operator; and
convert the color signals subjected to radiometric compensation to conversion from the device-independent color space to a display color space for display on the color display surface.

12. The electronic device of claim 7 , further comprising:
a display device driven by the processor to display the radiometric compensated signals on the colored display surface; and
a visual capture device coupled to the processor and directed toward the colored display surface.

13. A non-transitory computer readable medium configured to cause an associated computer to perform steps for radiometric compensation for displaying on a colored display surface color signals having a first color gamut in a color space, the steps comprising:
displaying on the colored display surface a set of control points of a known color;

acquiring the control points as displayed on the colored display surface, wherein the control points displayed on the colored display surface as acquired have at least one second color gamut which is misaligned with respect to the first color gamut due to the colored display surface being a colored surface;
evaluating the misalignment of the at least one second color gamut with respect to the first color gamut, wherein evaluating the misalignment comprises
generating a set of lines joining the control points to a middle grey color; and
sampling each line in the set from the middle grey color by finding a point common to the first color gamut and the at least one second color gamut displayable on the colored display surface;

calculating at least one color transformation operator as a function of the misalignment a transformation matrix from the control points to the common points found; and
applying the at least one color transforma

Assignees

• St Microelectronics Srl

Inventors

• Naccari Filippo
• Guarnera Mirko
• Bianco Simone
• Schettini Raimondo

Classifications

• H04N9/67

  for matrixing (camera processing pipelines for matrixing of colour signals H04N23/85) · CPC title

• H04N1/6088

  by viewing conditions, i.e. conditions at picture output · CPC title

• H04N9/3194

  including sensor feedback · CPC title

• G09G2320/0242

  Compensation of deficiencies in the appearance of colours · CPC title

• G06T7/90

  Determination of colour characteristics · CPC title