Image Processing Apparatus Sharpness Recovery Brightness Clipping
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Solution Overview
Problem
Image sharpness recovery processing in image forming apparatuses, such as inkjet printers, often results in brightness decrease in the high-frequency range due to the use of filters with reverse frequency characteristics for compensation, leading to sharpness degradation and clipping issues.
Innovation Solution
The proposed solution involves an image processing apparatus that performs gamma correction to address non-linearity in the image forming process, followed by separate recovery processing for low-frequency and high-frequency components using custom-designed filters to prevent brightness decrease and clipping, ensuring effective sharpness recovery without exceeding the expressible pixel range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sharpness recovery processing is performed on the input image with a filter having the reverse characteristic of the output image frequency characteristic, then sharpness degradation is compensated, but brightness decreases in the high-frequency range
Solution Approach 1:
The patent segments the sharpness recovery process into two distinct stages: first performing gamma correction to address non-linearity in the image forming process, then performing sharpness recovery processing on the gamma-corrected data. This segmentation allows the brightness compensation effect of gamma correction to counteract the brightness decrease caused by sharpness recovery filtering, thereby maintaining both sharpness and brightness in the final output.
2Illumination intensity
If gamma correction is performed before sharpness recovery processing, then non-linearity of input/output density is compensated and brightness decrease is suppressed, but processing order complexity increases
Solution Approach 1:
The patent applies gamma correction as a preliminary action before sharpness recovery processing. By pre-correcting the non-linearity of the image forming process and compensating for potential brightness decrease, the subsequent sharpness recovery filtering can be performed more effectively without causing clipping or excessive brightness loss. This preliminary action simplifies the overall processing requirements.
Data Source
AI summary
In order to implement preferred sharpness recovery processing for an image, an image processing apparatus which generates, based on input image data, halftone image data used for an image forming process of forming an image on a print medium. The apparatus converts the input image data into color material amount data used for the image forming process; performs, on the color material amount data, gamma correction to compensate for non-linearity of an input/output density in the image forming process; performs, on the color material amount data after the gamma correction, recovery processing to compensate for sharpness degradation of an image formed by the image forming process; and performs halftone processing on the color material amount data after the recovery processing to generate halftone image data.