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 20110310116A1
• Filed: 03/03/2010
• Published: 12/22/2011
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Muijs, Remco Theodorus Johannes
• Granted Patent: US 8,605,083 B2
• Time in Patent Office: Days
• US Class Current: 345/617
• 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 (V_RC) and a detail signal (V_D), followed by stretching separately the dynamic ranges for both signals, wherein the dynamic range for the regional contrast signal is stretched with a higher stretch ratio than the dynamic range for the detail signal. Preferably the stretch ratio for the detail signal is near 1 or preferably 1. In preferred embodiment 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. Method for converting input image data (V_in) into output image data ({tilde over (V)}₁, V_out) wherein the input image data (V_in) is split into at least two signals, a first signal (V_RC) comprising regional contrast data and a second signal (V_D) comprising detail data, the dynamic range of at least the first signal is stretched to provide a stretched first signal ({tilde over (V)}_RC), wherein the dynamic range of the first signal is stretched to a higher degree than applied to the second signal, and the stretched first ({tilde over (V)}_RC) and second ({tilde over (V)}_D) signals are combined in an output signal ({tilde over (V)}₁).

2. Method as claimed in claim 1, wherein the second signal (V_D) is made by subtracting the first signal (V_RC) from the image input data (V_in).

3. Method as claimed in claim 1, wherein the second signal (V_D) is not stretched.

4. Method as claimed in claim 1, wherein the upper value of the dynamic range for the combined stretched first and second signal ({tilde over (V)}₁) lies in a range corresponding to light intensities when displayed on a display of 500 to 1000 Nit.

5. Method as claimed in claim 1, wherein the dynamic range of the combined stretched first and second signal is bound by an upper value (W₀) and the input image signal (V_in) is analyzed (FHL(Vin)) to identify groups of pixels forming highlights in the image and wherein the pixel data for said identified groups of pixels are converted into a third signal (V_HL) such that the third signal covers a dynamic range (W_HDR-K_HDR) extending upwards above the said upper value (W₀) to a upper maximum pixel value (W_HDR) and wherein the third signal (V_HL) is combined with the combined stretched first and second signal ({tilde over (V)}₁) in an output signal (V_out).

6. Method as claimed in claim 5, wherein the upper maximum pixel value (W_HDR) lies in a range corresponding to light intensities when displayed on a display of above 1000 Nit.

7. Computer program comprising program code means for performing a method according to the present invention, when executed on a computer.

8. Image conversion unit for converting input image data into output image data, comprising a splitter for splitting the input image data (V_in) into at least two signals, a first signal (V_RC) comprising regional contrast data and a second signal (V_D) comprising detail data, a stretcher (3) to stretch the dynamic range of at least the first signal to provide a stretched first signal ({tilde over (V)}_RC), wherein the dynamic range of the first signal (V_RC) is stretched to a higher degree than applied to the second signal (V_D), and the unit comprises a combiner (5) to combine the stretched first ({tilde over (V)}_RC) and second ({tilde over (V)}_D) signals in an output signal ({tilde over (V)}₁).

9. Image conversion unit as claimed in claim 8, wherein the stretcher (3) is arranged such that the dynamic range of the combined stretched first and second signal is bound by an upper value (W₀) and the unit further comprises a identifier (7) to analyze the input image signal (V_in) to identify groups of pixels forming highlights in the image and a mapper (8) for mapping the pixel data for said identified groups of pixels into a third signal (V_HL) such that the third signal covers a dynamic range (W_HDR-K_HDR) extending upwards above the said upper value (W₀) to a upper maximum pixel value (W_HDR) and a combiner (9) for combining the third signal (V_HL) with the combined stretched first and second signal ({tilde over (V)}₁) in an output signal (V_out).

10. Image conversion unit as claimed in claim 9 wherein the stretcher (3) is arranged such that the upper value (W₀) of the dynamic range for the combined stretched first and second signal ({tilde over (V)}₁) lies in a range corresponding to light intensities when displayed on a display of 500 to 1000 Nit.

11. Image conversion unit as claimed in claim 9 wherein the mapper (8) is arranged such that the upper maximum pixel value (W_HDR) lies in a range corresponding to light intensities when displayed on a display of above 1000 Nit.

12. Image processing apparatus comprising receiving means for receiving input image data and an image conversion unit for converting the input image data into output image data as claimed in claim 8.

13. Display device comprising an image processing apparatus comprising:

receiving means for receiving input image data, an image conversion unit for converting input image data into output image data, as claimed in claim 8 and a display screen (91).

14. Display device comprising an image processing apparatus comprising receiving means for receiving input image data, an image conversion unit as claimed in claim 11, and a display screen, wherein the upper maximum pixel value corresponds to a value at or near a maximum of the dynamic range of the display screen (91).

15. Display device as claimed in claim 13, wherein the display device comprises an ambient illumination sensor (92) providing an output, wherein the output of the ambient illumination sensor (92) is an input for the stretcher (3).