Question

Which specific filter type is required to effectively remove salt-and-pepper noise while preserving the sharpness of image edges?

Accepted Answer

The specific filter type required to remove salt-and-pepper noise while preserving image edges is the median filter. Salt-and-pepper noise appears as random occurrences of black and white pixels scattered across an image, effectively acting as extreme outliers in pixel intensity. A median filter works by moving a window, known as a kernel, over every pixel in the image. For each position, the filter collects all the pixel values within that window, sorts them numerically, and replaces the center pixel with the median value of that sorted list. Because the median value is the middle number in a sorted sequence, it is statistically robust against outliers; the extreme high values of white noise or extreme low values of black noise are simply excluded from the selection process. Consequently, the filter successfully eliminates the noisy pixels without blurring the boundaries between objects. Unlike a mean filter, which calculates the average of neighboring pixels and spreads the noise into surrounding areas while blurring sharp edges, the median filter preserves the original intensity values of edges because those values remain the most frequent and central within the neighborhood, thus maintaining the sharpness and clarity of the image features.

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Which specific filter type is required to effectively remove salt-and-pepper noise while preserving the sharpness of image edges?