Colour filtering: colour bleeding and related accuracy issues

This paper studies colour filtering with particular reference to colour bleeding for median and mode filters. While confirming that multiple single-channel implementation gives especially serious colour bleeding, the paper goes on to argue that the conventional solution — of using the vector median — is over-strenuous for many types of application. In fact, instead of insisting that the output vector should be identical to one of the input vectors, it will often be better to output the vector that minimises the sum of distances in colour space to all the input vectors. This paper takes as example two uniform colour regions separated by a chasm of different colour and varying width — which provides the simplest instance in which colour bleeding can occur. The findings of the paper should be transferable to other applications such as mode filtering which use median filters as a first stage in the computation.