BTC image coding using two-dimensional median filter roots

Application of root signals of two-dimensional median filters to BTC (block truncation coding) is investigated. The 2D median filters considered are the 3×3 separable median (SM) filter and the 5-point cross window median (CWM) filter, as these two types of filters preserve image details well. Some properties of the root signal sets of these two filters are studied. It is shown that using the root signals of SM or CWM filters to perform BTC coding, little degradation results in the coded images, whereas the bits/pixel needed reduce to 1.69 or 1.81, respectively, compared to the standard BTC coding method whose bits/pixel are 2.0