SWiSH Max4 allows the user to assign a transparent color to images. The process works well. However, an inconsistent background color can introduce aberrations including jagged edges and areas where the original background remains. These aberrations can be improved by applying an inner blur filter.
The Flash animation below shows the different stages of applying transparency then adding a filter. The last image demonstrates how good it can look when used with a dark background. In this case, the filter color is altered to match the background color.