The Semi-flatten filter helps those in need of a solution to anti-aliasing indexed images with transparency.
In order to use this filter, the user must set the background color in the toolbox to the color that will be used for the destination of the image. For example, a black circle that will be saved as an indexed image for placement on a green web page would preclude a need to set the background color to the same color green as the web page.
With the background color set, the filter can be started. The filter will scan the edges of the selected layer and color them in a similar fashion to anti-aliasing, but using the selected background color instead of transparency.