Image processing

1. A method of processing an image comprising:

receiving compressed image data comprising encoded image data representing the image;

decoding the encoded image data to generate first decoded image data with a first bit precision;

processing the first decoded image data to generate second decoded image data with a second bit precision higher than the first bit precision;

applying a tone mapping operation to the second decoded image data to generate first tone mapped image data with the second bit precision; and

converting the first tone mapped image data to second tone mapped image data with the first bit precision.

2. The method according to claim 1 , wherein the second bit precision is represented by a first series of bits providing the first bit precision and an additional one or more bits providing additional bit precision to form the second bit precision and wherein the method comprises, when converting the first tone mapped image data to the second tone mapped image data:

improving the display quality of the image when represented by the first series of bits by deriving information from the additional one or more bits for pixels in at least part of the image and using the information to alter the first series of bits for pixels in the at least part of the image; and

discarding the additional one or more bits for the pixels in the at least part of the image.

3. The method according to claim 2 , wherein the improving the display quality of the image represented by the first series of bits comprises applying a dithering operation to the first tone mapped image data.

4. The method according to claim 1 , wherein the first bit precision is equal to a maximum bit precision displayable by a display device configured to display an output image based on the second tone mapped image data.

5. The method according to claim 1 , wherein the tone mapping operation is performed by a decoder capable of decoding compressed images encoded at the first bit precision and of decoding compressed images encoded at the second bit precision.

6. The method according to claim 1 , wherein the tone mapping operation reduces a dynamic range of the second decoded image data.

7. The method according to claim 1 , wherein the applying the tone mapping operation comprises applying a spatially-variant tone mapping to the second decoded image data.

8. The method according to claim 1 , wherein the processing the first decoded image data comprises applying one or more compression-noise reduction filters to the first decoded image data.

9. The method according to claim 8 , comprising applying one or more smoothing filters to reduce banding noise in the first decoded image data.

10. The method according to claim 8 , wherein the compressed image data is in an 8-bit JPEG (Joint Photographic Experts Group) format.

11. The method according to claim 1 , wherein:

the encoded image data comprises base image layer data representing a first dynamic range representation of the image; and

the compressed image data includes additional image layer data for generating a second dynamic range representation of the image, the second dynamic range being larger than the first dynamic range,

the method further comprising decoding the additional image layer data to generate decoded additional image layer data, the processing the first decoded image data comprising applying the decoded additional image layer data to generate the second decoded image data.

12. The method according to claim 11 , wherein the compressed image data is in a more than 8-bit JPEG (Joint Photographic Experts Group) XT format.

13. The method according to claim 1 , comprising compositing the second tone mapped image data with further display data representing at least one further display element to generate an output image.

14. A computing device comprising:

storage for storing compressed image data comprising encoded image data representing an image;

at least one processor communicatively coupled to the storage;

a bit precision enlargement module configured to:

decode the encoded image data to generate first decoded image data with a first bit precision; and

process the first encoded image data to generate second decoded image data with a second bit precision higher than the first bit precision;

a tone mapping module configured to apply a tone mapping operation to the second decoded image data to generate first tone mapped image data with the second bit precision; and

a bit precision reduction module configured to convert the first tone mapped image data to second tone mapped image data with the first bit precision.

15. The computing device of claim 14 , comprising a decoder module, the decoder module comprising the bit precision enlargement module, the tone mapping module and the bit precision reduction module.

16. The computing device of claim 14 , wherein the second bit precision is represented by a first series of bits providing the first bit precision and an additional one or more bits providing additional bit precision to form the second bit precision and wherein the bit precision reduction module is configured to, when converting the first tone mapped image data to the second tone mapped image data:

improve the display quality of the image when represented by the first series of bits by deriving information from the additional one or more bits for pixels in at least part of the image and using the information to alter the first series of bits for pixels in the at least part of the image; and

discard the additional one or more bits for the pixels in the at least part of the image.

17. The computing device of claim 16 , wherein the bit precision reduction module is configured to improve the display quality of the image when represented by the first series of bits by applying a dithering operation to the first tone mapped image data.

18. The computing device of claim 14 , comprising a display device configured to display an output image based on the second tone mapped image data,

wherein the first bit precision is equal to a maximum bit precision displayable by the display device.

19. The computing device of claim 14 , wherein the bit precision enlargement module is configured to apply one or more compression-noise reduction filters to the first decoded image data.

20. The computing device of claim 14 , comprising a decoder module, wherein:

the encoded image data comprises base image layer data representing a first dynamic range representation of the image;

the compressed image data includes additional image layer data for generating a second dynamic range representation of the image, the second dynamic range being larger than the first dynamic range;

the decoder module is configured to decode the additional image layer data to generate decoded additional image layer data; and

the bit precision enlargement module is configured to process the first decoded image data with the decoded additional image layer data to generate the second decoded image data.