Technology

A Spatial Median Filter for Noise Removal in Digital Images
James Church, Dr. Yixin Chen, and Dr. Stephen Rice Computer Science and Information System, University of Mississippi jcchurch@olemiss.edu,{ychen,rice}@cs.olemiss.edu

Abstract
In this paper, six different image filtering algorithms are compared based on their ability to reconstruct noiseaffected images. The purpose of these algorithms is to remove noise from a signal that might occur through the transmission of an image. A new algorithm, the Spatial Median Filter, is introduced and compared with the current image smoothing techniques. Experimental results demonstrate that the proposed algorithm is comparable to popular image smoothing algorithms. In addition, a modification to this algorithm is introduced to achieve more accurate reconstructions over other popular techniques.

Each of the algorithms covered can be applied to one dimensional as well as two dimensional signals. Figure 1 demonstrates five common filtering algorithms applied to an original image.

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1. Smoothing Algorithms
The inexpensiveness and simplicity of point-andshoot cameras, combined with the speed at which budding photographers can send their photos over the Internet to be viewed by the world, makes digital photography a popular hobby. With each snap of a digital photograph, a signal is transmitted from a photon sensor to a memory chip embedded inside a camera. Transmission technology is prone to a degree of error, and noise is added to each photograph. Significant work has been done in both hardware and software to improve the signal-to-noise ratio in digital photography. In software, a smoothing filter is used to remove noise from an image. Each pixel is represented by three scalar values representing the red, green, and blue chromatic intensities. At a pixel studied, a smoothing filter takes into account the pixels surrounding it in order to make a determination of a more accurate version...