Multiply by Alpha

The Multiply by Alpha filter ensures the transparency in an image is stored using a premultiplied alpha representation.

Some apps, such as compositing software and game engines, expect premultiplied alpha even though an image file format may store a non-premultiplied alpha representation by default.

When an image containing non-premultiplied alpha data is composited using a system that expects premultiplied alpha data, a halo effect may be noticeable along semi-transparent edges, for example.

The filter addresses this by converting to premultiplied alpha, enabling improved antialiasing along the edges.