Removal of impulse noise of anti-scatter grided images with modified switching median filters

For the images obtained by the flash radiography with an anti-scatter grid, impulse noises exist and need to be removed before further image processing. An improved switching median filter method is proposed in this paper for the task. In the method, the grayscales of a pixel and the median of its neiborhoods are utilized together to construct an impulse-noise-judger. If the value of the impulse-noise-judger is larger than a predefined threshold, the pixel is regarded as noise, and is replaced by the median. By implementing this operation on an initial image repeatedly, each with the same threshold, one can get satisfying result of impulse noise suppression. This is testified for simulated and real experiment images. The proposed method is superior to the standard median filter method in that it retains the original details of the images better.