Tone Mapping for Fine Feature Contrast Preservation

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Solution Overview

Problem

Tone mapping techniques often result in loss of contrast for fine features and unintended brightening of monotonic regions in images, leading to reduced image quality and increased power consumption.

Innovation Solution

Implementing a pixel contrast control block that applies a 2D low pass filter to the luma portion of an image, transforming low-frequency components via a tone mapping curve, and applying a 2D high pass filter to transform high-frequency components via a gain curve, while also multiplying histogram bins by their variance to prevent monotonic region brightening.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by stationary object

If tone mapping is applied to improve contrast and reduce power consumption, then power consumption is reduced and overall contrast is improved, but contrast of fine features is lost and monotonic regions are undesirably brightened

Engineering Contradiction:

Improvepower consumptionVSAvoidcontrast of fine features

Core Design Contradiction:

Use of energy by stationary objectVSManufacturing precision

Solution Approach 1:

The patent segments the image processing into frequency components using 2D low pass and high pass filters. Low-frequency components (smooth regions) are processed by tone mapping to reduce power consumption, while high-frequency components (fine features) are processed separately by a gain curve to preserve contrast, thus resolving the contradiction between power savings and fine feature preservation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different processing qualities to different regions: tone mapping is applied to low-frequency components for power efficiency, while high-frequency components receive enhanced processing through the gain curve to maintain fine detail contrast. This local differentiation resolves the contradiction by optimizing each frequency band according to its specific requirements

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If tone mapping is applied to improve overall contrast, then perceived image quality is improved, but contrast of high-frequency components is reduced

Engineering Contradiction:

Improveperceived image qualityVSAvoidcontrast of high-frequency components

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The patent divides the image into frequency bands using 2D low pass and high pass filters. The tone mapping curve is applied only to low-frequency components to improve overall perceived quality, while the gain curve is applied to high-frequency components to preserve their contrast, thus resolving the contradiction between overall quality improvement and fine detail preservation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the processing parameters differently for different frequency bands: tone mapping parameters are optimized for low-frequency components to improve perceived quality, while gain curve parameters are optimized for high-frequency components to maintain contrast, resolving the contradiction through parameter differentiation

Inventive Principle:

Principle #35Parameter changes

3Use of energy by stationary object

If tone mapping is applied to reduce backlight power consumption, then power consumption is reduced, but monotonic regions are undesirably brightened

Engineering Contradiction:

Improvebacklight power consumptionVSAvoidbrightness of monotonic regions

Core Design Contradiction:

Use of energy by stationary objectVSIllumination intensity

Solution Approach 1:

The patent segments the image processing to apply tone mapping only to low-frequency components, which contain the monotonic regions. By processing these separately from high-frequency components, the system can control the brightening effect locally, reducing overall power consumption while maintaining acceptable appearance in monotonic areas

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a gain curve as an intermediary processing step that acts on the high-frequency components after tone mapping. This intermediary processing compensates for any excessive brightening in monotonic regions by adjusting the high-frequency content, thus resolving the contradiction between power reduction and monotonic region appearance

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20240078648A1Tone Mapping for Preserving Contrast of Fine Features in an Image

Publication Date: 2024.03.07 APPLE INC

AI summary

This disclosure is directed towards tone mapping systems and methods that preserve contrast of fine features of an image and avoid brightening monotonic regions of the image. To preserve contrast and avoiding brightening of the monotonic regions, an image processing circuitry may include hardware that enables determining pixel statistics of an image, generating a tone mapping that is configured to adjust the color values of pixels in the image, and applying the tone mapping to at least the low frequency component of the image to produce an output image where the contrast of the fine details is preserved. In addition, the image processing circuitry may include hardware that enables adjusting the tone mapping based on variance bins in a histogram of pixel values and applying the adjusted tone mapping to produce an output image where the monotonic regions are not brightened.