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US 2008/0291287 A1Published application
Dynamic Range Compensation by Filter Cascade
AssigneeZoran Corporation
InventorItsik Dvir
Life of this patent
Estimating the term…
Abstract
A local method uses a cascade of multiple nonlinear edge preserving filters, and nonlinear pixel point operations, to calculate the pixel gain. Multiple low-pass filters are used, being applied to surrounding neighborhoods of the current pixel of narrow and of wide extent. The number of filter stages may be determined based on the image content. The coefficients used to combine a gray level image extracted from the input image with the ascending scale regions can be automatically extracted from high-pass filtered images of the ascending scale regions. Multiplying each color component of the input image by one or more pixel dependent gain or attenuation factors, using a nonlinear mapping function that can lighten shadow regions as well as darken bright regions, generates the output image.
Claims106
A method of compensating the dynamic range of a set of image data, comprising:
- receiving a measure of the image strength at a pixel of the set of image data;
- using the measure of the image strength at the pixel as the input of a first filter stage, where the first filter stage is a two dimensional filter formed from a first neighborhood of the pixel;
- using the measure of the image strength at the pixel and the output of the first filter stage as inputs of a second filter stage, where the second filter stage is a two dimensional filter formed from a second neighborhood of the pixel and wherein the second neighborhood is of greater extent than the first neighborhood;
- and
- determining one or more compensation factors for the pixel based on the output of the second filter stage.
2 more elements
A method of compensating the dynamic range of a set of image data, comprising:
- filtering though a number of cascaded filter stages a measure of the image strength at a pixel of the set of image data, wherein the number of stages is dependent on the set of image data and wherein each stage has larger support than the preceding stages;
- and
- determining one or more compensation factors for the pixel based on the output of the series of cascaded filters.
A method of compensating the dynamic range of a set of image data, comprising:
- filtering though a plurality of filter stages a measure of the image strength at a pixel of the set of image data, the stages including:
- a first stage having as input said measure and having as output a combination of said measure and a low-pass filtered version of said measure, the combination being dependent upon one or more parameters;
- and
- one or more second stages each having as input said measure and the output of the preceding stage and each having as output a combination of the output of the preceding stage and a low-pass filtered version of said measure, each of said combinations being dependent upon one or more parameters,
- wherein one or more of the parameters upon which one or more of said combinations are dependent is derived based upon the characteristics of the set of image data;
- and
- determining one or more compensation factors for the pixel based on the output last of the filter stages.
4 more elements
An image processing unit, including:
- an image intensity determination section to provide a measure of the image strength at a pixel of a set of image data;
- a filter section having:
- a first filter stage having as input the measure of the image strength at the pixel, where the first filter stage is a two dimensional filter formed from a first neighborhood of the pixel;
- and
- a second filter stage having as inputs the measure of the image strength at the pixel and the output of the first filter stage, where the second filter stage is a two dimensional filter formed from a second neighborhood of the pixel and wherein the second neighborhood is of greater extent than the first neighborhood;
- and
- a dynamic range compensation section to compensate input values of the pixel by one or more factors for the pixel based on the output of the second filter stage.
4 more elements
An image processing unit, including:
- an image intensity determination section to provide a measure of the image strength at a pixel of a set of image data;
- a filter section having as input the measure of the image strength at the pixel and comprising a plurality of cascaded filter stages, wherein each stage has larger support than the preceding stages and wherein the image processing unit determines the number of active stages based on the set of image data;
- and
- a dynamic range compensation section to compensate input values of the pixel by one or more factors for the pixel based on the output of the series of cascaded filters.
1 more element
An image processing unit, including:
- an image intensity determination section to provide a measure of the image strength at a pixel of a set of image data;
- a filter section having:
- a first stage having as input said measure and having as output a combination of said measure and a low-pass filtered version of said measure, the combination being dependent upon one or more parameters;
- and
- one or more second stages each having as input said measure and the output of the preceding stage and each having as output a combination of the output of the preceding stage and a low-pass filtered version of said measure, each of said
- combinations being dependent upon one or more parameters,
- wherein the image processing unit derives one or more of the parameters upon which one or more of said combinations are dependent based upon the characteristics of the set of image data;
- and
- a dynamic range compensation section to compensate input values of the pixel by one or more factors for the pixel based on the output of the last filter stage.
6 more elements
A method of compensating the dynamic range of a set of image data, comprising:
- receiving a measure of the image strength at a pixel of the set of image data;
- using the measure of the image strength at the pixel as the input of one or more cascaded filter stages, where each of the filter stages is a two dimensional filter formed from a corresponding neighborhood of the pixel;
- and
- determining a chromaticity factor for the pixel based on the output of the filter stages.
1 more element
An image processing unit, including:
- an image intensity determination section to provide a measure of the image strength at a pixel of a set of image data;
- a filter section having one or more cascaded filter stages, where each of the filter stages is a two dimensional filter formed from a corresponding neighborhood of the pixel;
- a dynamic range compensation section to compensate input values of the pixel by one or more chromaticity factors for the pixel based on the output of the second filter stage.
Dependencies are inferred from the claim text.