Image Processing Device Reducing Banding via Pre-Dither Noise
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Solution Overview
Problem
Electrophotographic printing devices often produce horizontal streaks or 'banding' in printed images due to issues with isolated dots and blank parts, leading to a decline in image quality, particularly when noise is added after converting image data into binary values using a dither matrix.
Innovation Solution
An image processing device that acquires and updates pixel color values by adding random numbers, then converts these values into binary values using a dither matrix, with the random number adding process occurring before thresholding to reduce the likelihood of isolated dots and blank parts being omitted or filled in.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise is added after converting image data into binary values using a dither matrix, then banding is suppressed, but isolated dots are omitted and blank parts are filled in
Solution Approach 1:
The patent applies preliminary action by adding random noise to the image data before the dithering process converts it to binary values. This pre-processing step modifies the pixel values in advance, ensuring that isolated dots maintain sufficient intensity and blank parts remain properly suppressed during subsequent thresholding, thereby preventing dot omission and blank part filling while still suppressing banding artifacts.
2Manufacturing precision
If a dither matrix with a pattern reducing isolated dots is used, then isolated dots and blank parts are reduced, but adding noise subsequently generates more isolated dots and blank parts
Solution Approach 1:
The patent reverses the conventional sequence by performing the noise addition action before dithering rather than after. This preliminary noise addition ensures that the random variations are incorporated into the pixel values that will subsequently undergo thresholding, preventing the generation of isolated dots and blank parts during the binary conversion process while maintaining control over existing isolated dots and blank parts.
Data Source
AI summary
An image processing device includes a storage unit, a processing unit, and a memory. The storage unit stores a dither matrix. The memory has instructions stored thereon that, when executed by the processing unit, cause the processing unit to function as: an acquiring unit that is configured to acquire an image including a plurality of pixels, each pixel having a color value; an updating unit that is configured to update a color value of at least one pixel by adding a random number to the color value; and a thresholding unit that is configured to convert the updated color value into a binary value by using the dither matrix.