Deriving a white-point for use in a multi-color light scene
When a light scene comprises multiple colors of light, not all white light is suitable for matching the scene. A method is provided such that a white point is determined for each color in a set of colors, to create a set of white points. A single white point is then determined based on the set of white points. This allows, for example, a user to select a light scene (e.g. a romantic scene featuring red colors) for a living room, such that lighting devices contributing to the scene emit colored light. A functional lighting device (e.g. reading light) can then emit white light, determined according to the method, to provide more functional light (e.g. light suitable for reading) that matches the scene (e.g. warm white instead of cold white).
1. A method of controlling a first lighting device, the method comprising:
receiving a set of colors, selected by a user and rendered by further lighting devices,
determining a set of white points comprising a white point for each of a plurality of colors in the set of colors previously selected by the user, the selection comprising selecting the set of colors via selecting an image from which the plurality of colors are extracted,
determining a single white point based on the set of white points, and
controlling the first lighting device to emit white light according to the determined single white point.
2. The method according to claim 1 , wherein determining a white point for at least one color in the set of colors comprises:
desaturating, in a predetermined color space comprising a black body line, the at least one color along a first path according to a first function; and
determining as a white point, for the at least one color, a color point along the first path at a predetermined distance from the black body line.
3. The method according to claim 2 , wherein the first function is a transfer function avoiding a predetermined region of color space.
4. The method according to claim 1 , wherein determining a white point for at least one color in the set of colors comprises:
desaturating, in a predetermined color space comprising a black body line, the at least one color along a first path according to a first function,
determining as an intermediate color point, for the at least one color, a color point along the first path at a predetermined distance from the black body line,
desaturating, in the predetermined color space, the intermediate color point along a second path according to a second function, and
determining as a white point, for the at least one color, a color point along the second path at a further predetermined distance from the black body line.
5. The method according to claim 4 , wherein the second function is arranged such that the second path is perpendicular to the black body line.
6. The method according to claim 1 , wherein the predetermined color space is the U′V′ color space.
7. The method according to claim 1 , wherein determining a single white point based on the set of white points comprises:
determining as a single white point, the average white point of the set of white points.
8. The method according to claim 7 , the method further comprising:
determining an intensity level for each color of the set of colors, wherein the average of the set of white points is a weighted average based on the determined intensity level.
9. The method according to claim 1 , the method further comprising:
storing the determined single white point and/or the received set of colors in a memory.
10. The method according to claim 1 , the method further comprising:
controlling the further lighting devices to emit colored light according to the received set of colors.
11. A non-transitory computer-readable medium comprising a computer program product arranged for performing the method according to claim 1 when run on one or more processors.
12. The method according to claim 1 , wherein said set of colors are colors of light present in an environment, and wherein the image is an image of the environment.
13. The method according to claim 12 , wherein the controlling the first lighting device to emit the white light comprises controlling the first lighting device to emit said white light in said environment.
14. A controller for controlling a first lighting device, the controller comprising:
a first interface arranged for receiving a set of colors, selected by a user and rendered by further lighting devices,
a second interface arranged for controlling the first lighting device, and
a processor coupled to the first and second interface, wherein the processor is arranged for:
determining a set of white points comprising a white point for each of a plurality of colors in the set of colors previously selected by the user, the selection comprising selecting the set of colors via selecting an image from which the plurality of colors are extracted,
determining a single white point based on the set of white points, and
controlling the first lighting device to emit white light according to the determined single white point.
15. The controller according to claim 14 , comprising a third interface for controlling the further lighting devices, and wherein the processor is further arranged for controlling the further lighting devices to emit colored light according to the received set of colors.
16. A lighting system comprising the controller according to claim 15 , the lighting system further comprising the first lighting device.
17. The controller according to claim 14 , wherein said set of colors are colors of light present in an environment, and wherein the image is an image of the environment.
18. The controller according to claim 17 , wherein the controlling the first lighting device to emit the white light comprises controlling the first lighting device to emit said white light in said environment.
19. A method of controlling a first lighting device, the method comprising:
receiving a set of color coordinate points, selected by a user and rendered by further lighting devices;
determining a set of white points comprising a respective white point for each corresponding color coordinate point of a plurality of color coordinate points in the set of color coordinate points previously selected by the user, wherein each respective white point, of said set of white points, is calculated by applying a function to the corresponding color coordinate point such that the calculated respective white point is independent of each other user-selected color coordinate point and such that the function approaches a black body line from said corresponding color coordinate point;
determining a single white point based on the set of white points; and
controlling the first lighting device to emit white light according to the determined single white point.
20. The method of claim 19 , wherein said single white point is different from each white point of said set of white points.