Character Pixel Color Correction for Higher Image Compression

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Solution Overview

Problem

Existing image compression methods for color images, particularly those with uneven luminance values, result in reduced compression efficiency and potential omission of image information, especially when dealing with handwritten documents.

Innovation Solution

An image processing apparatus that detects character pixels, corrects their colors based on determined information, divides the image into respective color segments, and generates compressed binary images without altering non-character pixel colors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If color reduction processing is performed on color image data to acquire color information and index color image, then compression efficiency is improved, but image information may be omitted when integrating approximate colors

Engineering Contradiction:

Improvecompression efficiencyVSAvoidimage information

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The patent segments the color space into multiple regions based on luminance values. Character pixels are identified and processed separately from non-character pixels. The color correction is applied selectively only to character pixels, preserving the original colors of non-character pixels while optimizing compression for character regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different color correction strategies to different regions of the image. Character pixels receive color correction based on their luminance values and position in the hue circle, while non-character pixels maintain their original colors. This local differentiation optimizes compression efficiency for text regions without sacrificing image information in other regions.

Inventive Principle:

Principle #3Local quality

2Productivity

If binary images of multiple colors are generated for compression, then compression efficiency improves with higher pixel continuity, but variation in luminance values of character pixels reduces continuity and compression efficiency

Engineering Contradiction:

Improvecompression efficiencyVSAvoidpixel continuity

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The patent changes the color parameters of character pixels by correcting their luminance values and assigning them to appropriate color regions in the hue circle. This parameter correction ensures that character pixels with varying original luminance values are unified into consistent color representations, thereby improving pixel continuity and compression efficiency.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12530735B2Image processing apparatus that improves compression efficiency of image data, method of controlling same, and storage medium

Publication Date: 2026.01.20 CANON KK

AI summary

An image processing apparatus that makes it possible to reproduce image information without omission and improves the compression efficiency of image data. Character pixels are detected from an image generated by reading an original using a scanner. Color information for use in compressing image data is determined. A color-converted image image is generated on which colors of the detected character pixels are corrected based on the color information, without changing colors of pixels other than the colors of the detected character pixels. The color-converted image is divided into images of respective colors of the color information. Compressed data of binary images is generated from the divided images of the respective colors.