High-pass filtering is a powerful but seldom used image enhancement technique. There are two main reasons for its unpopularity; very complex and time consuming work in frequency domain and difficult interpretation of the high-pass filtering products. In the frequency domain filter construction and image transformation is a multi-step process. This is a long and demanding process which requires very good knowledge of signal processing theory.

A High-pass filtered image has all rapid intensity changes enhanced, no matter how small they are. Most of them are imperceptible in original image. But the trade off is loss of low-frequency image content. The low-frequency content contains information about the far surroundings of the pixel - and necessary information for successful image interpretation. Without low-pass components an image looks like builders plaster when examined from exceptionally close up.

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