Method for converting input image data into output image data, image conversion unit for converting input image data into output image data, image processing apparatus, display device

• US 8,860,718 B2
• Filed: 11/12/2013
• Issued: 10/14/2014
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Muijs, Remco Theodorus Johannes
• Primary Examiner(s): Zarka, David
• Assistant Examiner(s): Vu, Khoa
• Application Number:
  US14/077,612
• Publication Number:
  US 20140071348A1
• Time in Patent Office: 336 Days
• Field of Search: None
• US Class Current: 345/419
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20028 Bilateral filtering
• CPC Class Codes: G06T 2207/20208 High dynamic range [HDR] image processing
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/90 Dynamic range modification of images or parts thereof
• CPC Class Codes: H04N 5/265 Mixing

Abstract

In a method, unit and display device, the input image signal is split into a regional contrast signal and a detail signal, followed by stretching separately the dynamic ranges for at least one of the signals. The dynamic range for the regional contrast signal is stretched with a higher stretch ratio than the dynamic range for the detail signal. The stretch ratio for the detail signal may be near 1 or 1. Further, highlights are identified, and for the highlights the dynamic range is stretched to an even higher degree than for the regional contrast signal.

Claims

1. A method for converting input image data of an image into output image data comprising the acts of:

splitting the input image data into a first signal having a first dynamic range and a second signal having a second dynamic range;

stretching the first dynamic range of the first signal to provide a stretched first signal having a stretched dynamic range, wherein the stretched dynamic range of the stretched first signal is higher than the second dynamic range of the second signal;

combining the stretched first signal and the second signal to from a combined signal having a dynamic range bound by an upper value;

analyzing the input image data to identity groups of pixels forming highlights in the image;

converting pixel data for said identified groups of pixels into a third signal having a dynamic range extending upwards above the upper value to an upper maximum pixel value;

combining the third signal with the combined signal to form the output image data; and

outputting the output image data.

2. The method of claim 1, wherein the second signal is made by subtracting the first signal from the image input data.

3. The method of claim 1, further comprising the act of stretching the second signal to form a stretched second signal for combining with the stretched first to form a stretched combined signal.

4. The method of claim 1, wherein an upper value of the dynamic range for the combined signal lies in a range corresponding to light intensities when displayed on a display of 500 to 1000 Nit.

5. The method of claim 1, wherein the upper maximum pixel value lies in a range corresponding to light intensities when displayed on a display of above 1000 Nit.

6. A non-transitory computer readable medium comprising computer instructions which, when executed by a computer, configure the computer to perform the acts of:

splitting input image data of an image into a first signal having a first dynamic range and a second signal having a second dynamic range;

stretching the first dynamic range of the first signal to provide a stretched first signal having a stretched dynamic range, wherein the stretched dynamic range of the stretched first signal is higher than the second dynamic range of the second signal;

combining the stretched first signal and the second signal to from a combined signal having a dynamic range bound by an upper value;

analyzing the input image data to identify groups of pixels forming highlights in the image;

converting pixel data for said identified groups of pixels into a third signal having a dynamic range extending upwards above the upper value to an upper maximum pixel value;

combining the third signal with the combined signal to form output image data; and

outputting the output image data.

7. The non-transitory computer readable medium of claim 6, wherein the second signal is made by subtracting the first signal from the image input data.

8. An image conversion unit for converting input image data of an image into output image data, comprising:

a splitter configured to split the input image data into a first signal having a first dynamic range and a second signal having a second dynamic range;

a stretcher configured to stretch the first dynamic range of the first signal to provide a stretched first signal having a stretched dynamic range;

wherein the stretched dynamic range of the stretched first signal is higher than the second dynamic range of the second signal;

a combiner configured to combine the stretched signal and the second signal to from a combined signal having a dynamic range hound by an upper value;

an identifier configured to analyze the input image signal and to identify groups of pixels forming highlights in the image;

a mapper configured to map pixel data for said identified groups of pixels into a third signal such that the third signal covers a dynamic range extending upwards above the said upper value to an upper maximum pixel value; and

a further combiner configured to combine the third signal with the combined signal to form the output image data.

9. The image conversion unit of claim 8, wherein the second signal is made by subtracting the first signal from the image input data.

10. The image conversion unit of claim 8, wherein the stretcher is arranged such that the upper value of the dynamic range for the combined signal lies in a range corresponding to light intensifies when displayed on a display of 500 to 1000 Nit.

11. The image conversion unit of claim 8, wherein the mapper is arranged such that the upper maximum pixel value lies in a range corresponding to light intensities when displayed on a display of above 1000 Nit.

12. A display device comprising an image processing apparatus comprising;

a receiver configured to receive input image data of an image;

an image conversion unit configured to convert the input image data into output image data; and

a display screen configured to render the output image data,

wherein, the image conversion unit comprises;

a splitter configured to split the input image data into a first signal having a first dynamic range and a second signal having a second dynamic range;

a stretcher configured to stretch the first dynamic range of the first signal to provide a stretched first signal having a stretched dynamic range, wherein the stretched dynamic range of the stretched first signal is higher than the second dynamic range of the second signal;

a combiner configured to combine the stretched signal and the second signal to from a combined signal having a dynamic range bound by an upper value;

an identifier configured to analyze the input image data and to identify groups of pixels forming highlights in the image;

a mapper configured to map pixel data for said identified groups of pixels into a third signal such that the third signal covers a dynamic range extending upwards above the said upper value to an upper maximum pixel value; and

a further combiner configured to combine the third signal with the combined signal to form the output image data.

13. The display device of claim 12, wherein the upper maximum pixel value corresponds to a value at or near a maximum of the dynamic range of the display screen.

14. The display device of claim 12, wherein the display device comprises an ambient illumination sensor providing an output, wherein the output of the ambient illumination sensor is an input for the stretcher.

15. An image conversion unit for converting input image data of an image into output image data, comprising:

a splitter configured to split the input image data into a first signal and a second signal;

a stretcher configured to stretch the first signal and the second signal differently, wherein a dynamic range of the first signal is stretched to a first stretched dynamic range and a dynamic range of the second signal is stretched to a second stretched dynamic range, the first stretched dynamic range of the stretched first signal being higher than the second dynamic stretched range of the second signal; and

a combiner configured to combine the stretched first and second signals to from a combined signal having a dynamic range bound by art upper value, wherein the combined signal is combined with a third signal having a third dynamic range higher than the upper value for forming the output image data.

16. The image conversion unit of claim 15, further comprising:

an identifier configured to analyze the input image signal and to identify groups of pixels forming highlights in the image;

a mapper configured to map pixel data for said identified groups of pixels into the third signal; and

a further combiner configured to combine the third signal with the combined signal to form the output image data.

17. The image eon version unit of claim 15, wherein the second signal is formed by subtracting the first signal from the image input data.

18. An image conversion unit for converting input image data of an image into output image data, comprising;

a splitter configured to split the input image data into a first signal having a first dynamic range and a second signal having a second dynamic range;

a stretcher configured to stretch the first signal for changing the first dynamic range to a stretched dynamic range which is higher than the second dynamic range of the second signal; and

a combiner configured to combine the stretched first and second signals to from a combined signal having a dynamic range bound by an upper value, wherein the combined signal is combined with a third signal having a third dynamic range higher than the upper value for forming the output image data.

19. The image conversion unit of claim 18, further comprising;

an identifier configured to analyze the input image signal and to identify groups of pixels forming highlights in the image;

a mapper configured to map pixel data for said identified groups of pixels into the third signal; and

a further combiner configured to combine the third signal with the combined signal to form the output image data.

20. The image conversion unit of claim 18, wherein the second signal is formed by subtracting the first signal from the image input data.