Image Processing Noise Reduction Using Local Color Uniformity
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Solution Overview
Problem
Conventional image processing methods for reducing color noise often result in color blurring, especially near edges, due to the need for large filter sizes to effectively suppress low-frequency noise, which increases circuit complexity and noise reduction is not sufficient at high-contrast edges.
Innovation Solution
An image processing apparatus that determines the uniformity of pixel areas to set appropriate reference areas for noise reduction, using primary and secondary areas to correct pixel values based on evaluation values, thereby reducing noise without causing color blurring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If smoothing processing or order statistics filter is used to reduce color noise, then color noise reduction effect is improved, but circuit scale increases due to the need for large number of taps
Solution Approach 1:
The patent applies different processing strategies to different regions of the image based on color uniformity determination. For pixels in uniform color areas, a predetermined reference area is used for noise reduction, while for pixels in non-uniform areas, a dynamically determined reference area is used. This local differentiation allows effective noise reduction without requiring large filter sizes across the entire image, thus reducing circuit complexity.
2Reliability
If filter processing is performed after reducing input image to reduce color noise, then noise reduction effect is improved, but color blurring occurs at color area boundaries due to enlargement
Solution Approach 1:
The patent determines color uniformity for each pixel and selects different reference area strategies accordingly. Pixels in uniform color regions use a predetermined reference area that provides sufficient noise reduction, while pixels near color boundaries use a dynamically determined reference area that adapts to the local color transitions. This prevents color blurring at boundaries while maintaining noise reduction effectiveness in uniform regions.
Solution Approach 2:
The reference area is not fixed but dynamically determined based on the color uniformity assessment of each pixel. The system adaptively adjusts the reference area size and composition according to local image characteristics, allowing the noise reduction processing to be optimized for each specific region rather than applying a uniform approach throughout the image.
3Productivity
If color noise reduction is performed without reducing input image, then processing efficiency is improved, but color blurring becomes more likely at boundary portions due to large range processing
Solution Approach 1:
The patent processes each pixel independently by determining its local color uniformity and selecting an appropriate reference area. This avoids the need for large-range filter processing while still achieving effective noise reduction. The local processing approach maintains color accuracy at boundaries because each pixel's reference area is carefully selected to exclude pixels from different color regions.
Data Source
AI summary
Color noise is reduced while suppressing the occurrence of color blurring in the vicinity of an edge. An image processing apparatus including: a first determination unit configured to determine whether or not a first area consisting of a plurality of pixels including a pixel of interest is an area in a uniform color for the pixel of interest in input image data; a second determination unit configured to determine whether or not a second area, different from the first area, consisting of a plurality of pixels including the pixel of interest is an area in a uniform color; a setting unit configured to set a reference area consisting of the pixel of interest and adjacent pixels of the pixel of interest for the pixel of interest; and a first correction unit configured to correct the pixel value of the pixel of interest to a value for which noise has been reduced based on the pixel value of the pixel included in the reference area.