Image Processing Apparatus Gray Highlight Removal 3D-LUT
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Solution Overview
Problem
Conventional image processing techniques struggle to accurately reproduce color highlights while removing show-through and background images, often resulting in the removal of unwanted highlights, including color highlights.
Innovation Solution
An image processing apparatus and method utilizing a combination of 3D-LUT and 1D-LUT, where the 3D-LUT converts signal values closer to white into even whiter values, and the 1D-LUT sets signal values greater than a predetermined value to white, allowing for the removal of gray highlights without affecting color highlights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If under-color removal is enhanced to remove show-through and background images, then background removal is improved, but color highlights are also removed
Solution Approach 1:
The invention segments the color space into distinct regions: a first region for gray highlights (achromatic colors) and a second region for color highlights (chromatic colors). By applying different processing strategies to each segment, the system removes gray highlights while preserving color highlights, resolving the contradiction between background removal and highlight preservation.
Solution Approach 2:
The invention applies different quality characteristics to different parts of the color space. The first region (gray highlights) is processed with aggressive under-color removal to eliminate show-through, while the second region (color highlights) is processed with preservation characteristics to maintain highlight information. This local differentiation resolves the contradiction by allowing aggressive removal only where appropriate.
2Loss of information
If determination information regarding color highlight region is used to preserve color highlights, then color highlight reproduction is improved, but device complexity increases due to switching 1D-LUT
Solution Approach 1:
The invention merges the functions of multiple 1D-LUTs into a single 3D-LUT that processes all color values in one operation. The 3D-LUT is constructed with specific characteristics: the first region (gray highlights) has conversion characteristics that remove gray highlights, while the second region (color highlights) has characteristics that preserve them. This unified approach eliminates the need for determination information and LUT switching, reducing device complexity while maintaining color highlight preservation.
Solution Approach 2:
The single 3D-LUT serves multiple functions simultaneously: it performs color space conversion, removes gray highlights, and preserves color highlights all in one operation. This multi-functional approach eliminates the need for separate determination and processing steps, simplifying the device while achieving the desired outcome.
3Device complexity
If a single 1D-LUT is used for under-color removal, then processing simplicity is maintained, but gray highlights cannot be removed without affecting color highlights
Solution Approach 1:
The invention transitions from one-dimensional 1D-LUT processing to three-dimensional 3D-LUT processing. This dimensional change enables the system to distinguish between gray and color highlights based on their position in the three-dimensional color space. The 3D-LUT can identify achromatic colors (gray highlights) versus chromatic colors (color highlights) and apply appropriate processing to each, enabling gray highlight removal while maintaining processing efficiency.
Data Source
AI summary
An image processing apparatus has a first color conversion unit that converts a signal value at an achromatic grid point in a first color space among achromatic grid points in a color space, the signal value being closer to white than a first predetermined signal value, into a signal value that is even closer to white, and a second color conversion unit that converts a signal value at a grid point among grid points in the color space, the signal value being closer to white than a second predetermined signal value, into white are provided. The image processing apparatus converts a signal value of an input image using the first color conversion unit, and thereafter converting the signal value using the second color conversion unit.