Method and apparatus for digital image defect correction and noise filtering

Abstract

An adaptive median filter ( ) provides dynamic detection and correction of digital image defects which are caused by defective or malfunctioning elements of a radiation detector array ( ). The adaptive median filter receives ( ) lines of pixel values of a digital image that may have defects and a user-defined defect threshold. The lines of pixel values are scanned on a pixel-by-pixel basis using a kernel of n×n pixels, where the kernel contains the candidate pixel being examined ( ). Each kernel is numerically reordered ( ) and a median value is calculated ( ). A defect threshold value is calculated by multiplying the user-defined defect threshold criteria and the candidate pixel value ( ). A reference value is calculated by subtracting the candidate pixel value and the median value ( ). The reference value is compared to the defect threshold value ( ). The candidate pixel value is replaced by the median value ( ) if it differs from the median value by more than the predefined defect threshold, e.g., 20%. The adaptive median filter is particularly effective in detecting and correcting double line and double column defects in digital images. In addition, the filter minimizes image blurring and maintains image resolution by filtering only defective pixels.