US 9,437,171 B2Granted

Local tone mapping for high dynamic range images

AssigneeTexas Instruments Incorporated

InventorsRajesh Narasimha, Aziz Umit Batur

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Abstract

A method of local tone mapping of a high dynamic range (HDR) image is provided that includes dividing a luminance image of the HDR image into overlapping blocks and computing a local tone curve for each block, computing a tone mapped value for each pixel of the luminance image as a weighted sum of values computed by applying local tone curves of neighboring blocks to the pixel value, computing a gain for each pixel as a ratio of the tone mapped value to the value of the pixel, and applying the gains to corresponding pixels in the HDR image. A weight for each value is computed based on distance from the pixel to the center point of the block having the local tone curve applied to compute the value and the intensity difference between the value of the pixel and the block mean pixel value.

Claims20

Dependent claims

A method of local tone mapping of a high dynamic range (HDR) image, the method comprising:

generating, with one or more processors, a luminance image of the HDR image;
dividing, with the one or more processors, the luminance image into overlapping blocks and computing a local tone curve for each block;
computing, with the one or more processors, a tone mapped value for each pixel of the luminance image as a weighted sum of N values computed by applying local tone curves of N neighboring blocks of the pixel to a value of the pixel, wherein a weight for each value of the N values is computed based on a distance from the pixel to a center point of the block having the local tone curve applied to compute the value of the N values and an intensity difference between the value of the pixel and a mean pixel value of the block, wherein N is a positive integer;
computing, with the one or more processors, a gain for each pixel of the luminance image as a ratio of the tone mapped value to the value of the pixel;
and
applying, with the one or more processors, the computed gains to corresponding pixels in the HDR image to generate a tone-mapped HDR image.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/098,243Filed 5 Dec 2013 · us provisional application
Priority: 5 Dec 2012
Published: US 2014/0152686 A15 Jun 2014
Granted: 6 Sep 2016
Term ends: Not estimatedThe source records don’t support an estimate.

Classification16 codes

G09G 5/377
Details of the operation on graphic patterns: for mixing or overlaying two or more graphic patterns
G06T 5/50
Image enhancement or restoration: using two or more images, e.g. averaging or subtraction
G06T 5/92
Dynamic range modification of images or parts thereof: based on global image properties
G06T 5/94
Dynamic range modification of images or parts thereof: based on local image properties, e.g. for local contrast enhancement

Family

Application61/733,513Us provisional application · filed 5 Dec 2012
US 2014/0152686 A1Pre-grant publication · published 5 Jun 2014
US 9,437,171 B2This patent

From the US filing history. Foreign family members aren’t listed.

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