Deposterizing Digital Images Using Partial Differential Equations

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Solution Overview

Problem

Digital images that have been posterized lack pixel depth and detail, and existing image-processing techniques to address this issue either produce limited results or introduce artifacts, with blurring methods causing information loss and failing to completely remove posterization.

Innovation Solution

A system that deposterizes images by generating new color values from the full range of possible values, using partial differential equations to smooth out 'steps' while maintaining constraints that allow the image to be reposterized to its original state, avoiding excessive blurring and information loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If blurring techniques are applied to remove posterization, then posterization artifacts are reduced, but image details are lost

Engineering Contradiction:
Improveposterization artifactsVSAvoidimage details
Core Design Contradiction:
Object-generated harmful factorsVSLoss of information

Solution Approach 1:

The patent applies partial differential equations (specifically the Laplace equation) to transform discrete posterized color values into continuous color values. This mathematical transformation smoothly interpolates between discrete posterization levels, eliminating visible steps while preserving fine image details that would otherwise be lost in traditional blurring operations.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent replaces traditional mechanical blurring operations with a mathematical field-based approach using partial differential equations. Instead of physically smoothing pixel values through convolution or averaging, the system uses the Laplace equation to generate a continuous potential field that naturally eliminates discontinuities while preserving structural information.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If image-sharpening tools are applied to posterized images, then image sharpness is improved, but unnatural artifacts are produced

Engineering Contradiction:
Improveimage sharpnessVSAvoidunnatural artifacts
Core Design Contradiction:
Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

Instead of applying sharpening operations to an already posterized image (which exacerbates artifacts), the patent inverts the approach by first removing posterization through continuous value transformation, then the image can be naturally sharpened without the interference of discrete color steps. This prevents the outlining and unnatural effects described in the background.

Inventive Principle:
Principle #13The other way round (Inversion)

3Object-generated harmful factors

If Gaussian blur is applied to completely remove posterization, then posterization is eliminated, but excessive blurring occurs

Engineering Contradiction:
ImproveposterizationVSAvoidimage detail preservation
Core Design Contradiction:
Object-generated harmful factorsVSManufacturing precision

Solution Approach 1:

The patent transforms the discrete parameter space of posterized images into a continuous parameter space using partial differential equations. This allows complete elimination of posterization artifacts without requiring excessive blur, as the mathematical transformation inherently smooths transitions while preserving local variations and fine details.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS7471824B1Method and apparatus for deposterizing a posterized digital image
Publication Date: 2008.12.30 ADOBE INC
  • US7471824B1 patent drawing
  • US7471824B1 patent drawing
  • US7471824B1 patent drawing

AI summary

One embodiment of the present invention provides a system that deposterizes a posterized image. During operation, the system receives a posterized image, wherein pixels in the posterized image have color values that belong to a set of posterized color values, which is a subset of a set of possible color values for the deposterized image. Next, the system generates a deposterized image from the posterized image, wherein color values in the deposterized image are not restricted to the set of posterized color values and instead can be selected from the entire set of possible color values to reduce artifacts caused jumps in color values that arise from posterization. While generating the deposterized image, the system selects color values for pixels in the deposterized image so that the deposterized image can be reposterized to restore the original posterized image.