Image Processing Apparatus Brightness Correction Edge Detection

The patent divides the background region into multiple segments along the main scan line direction and uses multiple main scan lines (first, second, and third main scan lines) to capture brightness variations at different positions. This segmentation allows the system to detect and correct local brightness fluctuations caused by inclination or flexure without requiring a complex correction model, thereby improving edge point detection accuracy while maintaining reasonable process complexity.

The patent transitions from using a single main scan line to utilizing multiple main scan lines (first, second, and third) at different positions relative to the document region. This dimensional expansion from one scan line to three scan lines provides additional information about brightness variations across the background region, enabling more accurate correction of brightness fluctuations while maintaining computational efficiency.

The patent performs preliminary brightness correction on the background region by comparing the first main scan line with the second and third main scan lines before edge detection is performed. This preliminary action removes the brightness fluctuations caused by inclination or flexure, creating a normalized background that allows the use of a smaller, more sensitive threshold for edge detection without risking false detections, thus simultaneously improving both reliability and precision.

The patent uses the brightness information from the second and third main scan lines as feedback to correct the brightness values on the first main scan line. This feedback mechanism continuously adjusts the brightness correction based on the actual measured brightness variations, enabling the system to maintain optimal edge detection parameters and achieve both high reliability and precision.

The patent applies local quality correction by using the second and third main scan lines (which are locally adjacent to the first main scan line) to correct brightness variations only in the specific regions where fluctuations occur. This localized approach focuses computational resources on the most critical areas near the document region rather than processing the entire background uniformly, thereby achieving high brightness stability with reduced processing time.

The patent uses a partial action approach by selecting only the necessary number of main scan lines (first, second, and third) to achieve adequate brightness correction. Rather than using all available scan lines or performing exhaustive correction, the system identifies and corrects only the most significant brightness variations using a limited set of strategically selected scan lines, balancing correction effectiveness with processing efficiency.