Error Diffusion Region Boundary Buffering for Image Quality
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Solution Overview
Problem
Error diffusion processing in image printing leads to dot pattern mismatch and thread-like image degradation at the joints of divided regions due to inadequate error diffusion between regions, resulting in discontinuous dot patterns.
Innovation Solution
An image processing apparatus and method that utilizes two error holding units to manage and spread errors appropriately between regions, determining whether to reference or store errors based on the pixel position, ensuring continuous error diffusion across region boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If error diffusion processing is performed after region division to reduce memory cost, then memory storage capacity requirement is reduced, but dot pattern mismatch and thread-like image degradation occur at region joints
Solution Approach 1:
The image is divided into multiple regions for processing, allowing memory to store only the current region data rather than the entire image. This segmentation enables low-cost home printers to perform error diffusion processing without requiring expensive full-size memory, while the patent addresses the joint quality issue through specialized error buffering at region boundaries.
Solution Approach 2:
A buffer memory is introduced as an intermediary component to store quantization errors at region boundaries. This buffer acts as a mediator that transfers error information between adjacent regions, ensuring continuous error diffusion processing across region joints and preventing dot pattern mismatch without requiring full-size memory.
2Reliability
If a buffer memory is introduced to spread errors between regions, then continuity of error diffusion processing at region joints is maintained, but device complexity increases
Solution Approach 1:
Instead of uniformly processing all pixels, the patent applies specialized error buffering only at region boundary pixels. The buffer memory stores quantization errors specifically for pixels at the end of one region and the beginning of the next region, maintaining error diffusion continuity only where needed at joints, while regular interior pixels use standard error diffusion processing.
Solution Approach 2:
The buffer memory stores errors for a limited number of pixels at region boundaries rather than all pixels. This partial action approach maintains error diffusion continuity at critical joint locations without the complexity of managing buffers for the entire image, balancing reliability improvement with acceptable device complexity.
Data Source
AI summary
When the pixel of interest exists at a pixel position where reference of an error buffer is necessary, a quantization error generated in a region having undergone error diffusion processing is obtained from the error buffer. A quantization error generated in error diffusion processing in a region containing the pixel of interest is obtained from an error memory. Diffusion errors are calculated from the quantization errors using an error diffusion matrix. The value of the pixel of interest and the diffusion errors are added, and the addition value is quantized into the quantization value of the pixel of interest. The difference between the quantization value and the addition value is calculated as a quantization error to be stored in the error memory. When the pixel of interest exists at a pixel position where write in the error buffer is necessary, the quantization error is stored in the error buffer.