ESTABLISHING ONE-DIMENSIONAL TRANSFORMS

• US 20100123942A1
• Filed: 11/20/2008
• Published: 05/20/2010
• Est. Priority Date: 11/20/2008
• Status: Active Grant

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Fowler, John H.
• Granted Patent: US 8,248,678 B2
• Time in Patent Office: Days
• US Class Current: 358/518
• CPC Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence
• CPC Class Codes: H04N 1/603 controlled by characteristics of the picture signal generator or the picture reproducer

Abstract

One-dimensional color transforms are automatically calculated by identifying at least one device-independent color space curve, at least one device-dependent color space curve and at least one association amongst the curves. Depending on the motivation for creating the one-dimensional transform, different curves, associations and calculations can be used to generate the transforms without obtaining additional device measurements or iteratively adjusting transform values.

Claims

1. A method for creating one-dimensional transforms for a device, the method comprising:

selecting at least one device-dependent color space (DDC) color for transformation;

determining a motive for creating one-dimensional transforms for the at least one DDC color;

associating points from at least one device independent color space (DIC) curve and at least one DDC curve based on the selected DDC colors; and

creating at least one one-dimensional transform for the selected DDC colors based on the motive and the associated points.

2. A method according to claim 1 wherein creating the one-dimensional transforms comprises creating without iterating to reduce a color error while creating the one-dimensional transforms.

3. A method according to claim 1 wherein creating comprises creating without collecting additional device response measurements.

4. A method according to claim 1 wherein determining the motive comprises determining a need for adjusting a response of the device.

5. A method according to claim 4 wherein selecting at least one DDC color for transformation comprises selecting at least three DDC colors.

6. A method according to claim 5 wherein associating points from at least one DIC curve and at least one DDC curve comprises:

identifying a DIC curve as a basis for adjusting the device response; and

identifying a DDC curve corresponding to the DIC curve by identifying an associated DDC point for each of a selection of points on the DIC curve using a model of an expected response for the device.

7. A method according to claim 6 wherein identifying the DIC curve comprises identifying a neutral DIC curve.

8. A method according to claim 6 wherein creating the one-dimensional transforms for the selected DDC colors comprises:

selecting a first adjustment point on the DIC curve;

selecting a first adjustment vector for the adjustment point;

determining an adjustment extent along the DIC curve surrounding the adjustment point;

identifying a plurality of DDC adjustment vectors for a plurality of DDC adjustment points on the DDC curve based on the DIC adjustment vector, the adjustment extent along the DIC curve and a model of the expected device response; and

creating one-dimensional transforms for the selected DDC colors based on the plurality of DDC adjustment vectors for the plurality of DDC adjustment points.

9. A method according to claim 8 wherein selecting the first adjustment vector comprises selecting a vector to modify the chromaticity of the adjustment point.

10. A method according to claim 8 wherein selecting the first adjustment vector comprises selecting a vector to modify the lightness of the adjustment point.

11. A method according to claim 8 wherein identifying the plurality of DDC adjustment vectors for the plurality of DDC adjustment points on the DDC curve comprises:

identifying a plurality of additional DIC adjustment points along the adjustment extent;

calculating a plurality of additional DIC adjustment vectors for the plurality of additional DIC adjustment points wherein calculating each additional adjustment vector comprises maintaining the direction of the first adjustment vector and assigning a reduced first adjustment vector magnitude based on the distance of the additional adjustment point from the first adjustment point; and

identifying the plurality of DDC adjustment vectors for the plurality of DDC adjustment points based on the plurality of DIC adjustment points and the corresponding plurality of DIC adjustment vectors.

12. A method according to claim 8 wherein identifying the plurality of DDC adjustment vectors for the plurality of DDC adjustment points on the DDC curve comprises:

identifying a first DDC adjustment vector for a first DDC adjustment point based on the first adjustment point and the first adjustment vector;

identifying a plurality of additional DDC adjustment points in relation to the first DDC adjustment point; and

calculating a plurality of additional DDC adjustment vectors for the plurality of additional DDC adjustment points wherein calculating each additional adjustment vector comprises maintaining the direction of the first DDC adjustment vector and assigning a reduced first DDC adjustment vector magnitude based on the distance of the additional DDC adjustment point from the first DDC adjustment point.

13. A method according to claim 11 wherein identifying a DDC adjustment vector for a DDC adjustment point based on a DIC adjustment point and a corresponding DIC adjustment vector comprises:

identifying the DDC adjustment point based on the DIC adjustment point and a model of the expected device response;

identifying the DDC vector endpoint based on the DIC adjustment point offset by the DIC adjustment vector and a model of the expected device response; and

calculating the DDC adjustment vector as the difference between the DDC vector endpoint and the DDC adjustment point.

14. A method according to claim 8 wherein creating one-dimensional transforms for the selected DDC colors comprises creating a plurality of transform tuples for each selected color wherein each transform tuple comprises an input tint and an output tint for the selected color and wherein each transform tuple is based on a DDC adjustment point and a corresponding DDC adjustment vector.

15. A method according to claim 14 wherein creating the transform tuple for the selected color comprises:

selecting the coordinate for the selected color from the DDC adjustment point as input tint; and

calculating the output tint as the input tint plus the value for the selected color from the DDC adjustment vector.

16. A method according to claim 1 wherein determining the motive comprises determining a need for a destination device to emulate the response of a source device.

17. A method according to claim 16 wherein selecting at least one DDC color for transformation comprises selecting at least three DDC colors.

18. A method according to claim 17 wherein associating points from at least one DIC curve and at least one DDC curve comprises:

identifying neutral DIC curves corresponding to both the source and destination devices;

associating points on the source neutral DIC curve with points on the destination neutral DIC curve based on a DIC characteristic;

identifying source and destination DDC curves corresponding to the respective neutral DIC curves by identifying an associated DDC point for each of a selection of points on a respective DIC curve using a model of an expected response for the respective device; and

associating points on the source DDC curve with points on the destination DDC curve based on the association between source and destination neutral DIC points and the association between DIC and DDC points for respective devices.

19. A method according to claim 18 wherein associating points on the source neutral DIC curve with points on the destination neutral DIC curve based on the DIC characteristic comprises one of:

associating points having the same normalized L* values;

associating points having the same normalized distance along respective DIC curves; and

associating points by incorporating human perception into a DIC curve mapping.

20. A method according to claim 18 wherein creating one-dimensional transforms for the selected DDC colors comprises creating a plurality of transform tuples for each selected color wherein each transform tuple comprises an input tint and an output tint for the selected color and wherein each transform tuple is based on an associated source and destination DDC point.

21. A method according to claim 14 wherein creating a transform tuple for the selected color comprises:

selecting the coordinate for the selected color from the source DDC point as input tint; and

selecting the coordinate for the selected color from the destination DDC point as output tint.

22. A method according to claim 16 wherein selecting at least one DDC color for transformation comprises selecting only one DDC color common to both source and destination devices.

23. A method according to claim 22 wherein associating points from at least one DIC curve and at least one DDC curve comprises:

identifying a common DDC curve comprising a plurality of tint values for the one DDC color common to both source and destination devices;

identifying source and destination DIC curves corresponding to the common DDC curve by identifying respective DIC points for each of a selection of tint values on the common DDC curve using models of an expected response for the respective devices; and

associating points on the source DIC curve with points on the destination DIC curve based on a DIC characteristic.

24. A method according to claim 22 wherein creating one-dimensional transforms for the one DDC color comprises creating a plurality of transform tuples wherein each transform tuple comprises an input tint and an output tint for the one DDC color and wherein each transform tuple is based on a source input tint and the association between points on the source and destination DIC curves and the association between points on the respective DIC and DDC curves.

25. A method according to claim 24 wherein creating a transform tuple for the one DDC color comprises:

selecting the source input tint as the input tint;

identifying source DIC point associated with the source input tint;

identifying the destination DIC point associated with the source DIC point; and

selecting the destination input tint associated with the destination DIC point as the output tint.

27. A medium carrying a set of computer-readable signals comprising instructions which, when executed by a data processor, cause the data processor to execute a method according to claim 1.

26. An apparatus for creating one-dimensional transforms for a device, the apparatus comprising:

a computer system with an interface operative to;

select at least one DDC color for transformation; and

identify a motive for creating one-dimensional transforms for the at least one DDC color; and

a computer system with a module operative to;

obtain information derived from inputs to the interface;

associate points from at least one DIC curve and at least one DDC curve based on the selected DDC colors; and

creating one-dimensional transforms for the selected DDC colors based on the motive and the associated points.